MIT News - Oceanography and ocean engineeringhttps://news.mit.edu/topic/mitoceans-rss.xml
MIT News is dedicated to communicating to the media and the public the news and achievements of the students, faculty, staff and the greater MIT community.enTue, 06 Nov 2018 11:19:23 -0500Oceanographers produce first-ever images of entire cod shoalshttps://news.mit.edu/2018/oceanographers-first-images-cod-shoals-1106
Wide-ranging acoustic images could help researchers identify populations on the brink of collapse.Tue, 06 Nov 2018 11:19:23 -0500Jennifer Chu | MIT News Officehttps://news.mit.edu/2018/oceanographers-first-images-cod-shoals-1106<p>For the most part, the mature Atlantic cod is a solitary creature that spends most of its time far below the ocean’s surface, grazing on bony fish, squid, crab, shrimp, and lobster — unless it’s spawning season, when the fish flock to each other by the millions, forming enormous shoals that resemble frenzied, teeming islands in the sea.</p>
<p>These massive spawning shoals may give clues to the health of the entire cod population — an essential indicator for tracking the species’ recovery, particularly in regions such as New England and Canada, where cod has been severely depleted by decades of overfishing.</p>
<p>But the ocean is a murky place, and fish are highly mobile by nature, making them difficult to map and count. Now a team of oceanographers at MIT has journeyed to Norway — one of the last remaining regions of the world where cod still thrive — and used a synoptic acoustic system to, for the first time, illuminate entire shoals of cod almost instantaneously, during the height of the spawning season.</p>
<p>The team, led by Nicholas Makris, professor of mechanical engineering and director of the Center for Ocean Engineering, and Olav Rune Godø of the Norwegian Institute of Marine Research, was able to image multiple cod shoals, the largest spanning 50 kilometers, or about 30 miles. From the images they produced, the researchers estimate that the average cod shoal consists of about 10 million individual fish.</p>
<p>They also found that when the total population of cod dropped below the average shoal size, the species remained in decline for decades.</p>
<p>“This average shoal size is almost like a lower bound,” Makris says. “And the sad thing is, it seems to have been crossed almost everywhere for cod.”</p>
<p>Makris and his colleagues have published their results today in the journal <em>Fish and Fisheries.</em></p>
<p><strong>Echoes in the deep</strong></p>
<p>For years, researchers have attempted to image cod and herring shoals using high-frequency, hull-mounted sonar instruments, which direct narrow beams below moving research vessels. These ships traverse a patch of the sea in a lawnmower-like pattern, imaging slices of a shoal by emitting high-frequency sound waves, and measuring the time it takes for the signals to bounce off a fish and back to the ship. But this method requires a vessel to move slowly through the waters to get counts; one survey can take many weeks to complete and typically samples only a small portion of any particular expansive shoal, often completely missing shoals between survey tracks and never capturing shoal dynamics</p>
<p>The team made use of the Ocean Acoutic Waveguide Remote Sensing, or OAWRS system, an imaging technique developed at MIT by Makris and co-author Purnima Ratilal, which emits low-frequency sound waves that can travel over a much wider range than high-frequency sonar. The sound waves are essentially tuned to bounce off fish, in particular, off their swim bladder — a gas-filled organ that reflects sound waves — like echoes off a tiny drum. As these echoes return to the ship, researchers can aggregate them to produce an instant picture of millions of fish over vast areas.</p>
<p><strong>Making passage</strong></p>
<p>In February and March of 2014, Makris and a team of students and researchers headed to Norway to count cod, herring, and capelin during the height of their spawning seasons. They towed OAWRS aboard the Knorr, a U.S. Navy research vessel that is operated by the Woods Hole Oceanographic Institution and is best known as the ship aboard which researchers discovered the remnants of the Titanic.</p>
<p>The ship left Woods Hole and crossed the Atlantic over two weeks, during which time the crew continuously battled storms and choppy winter seas. When they finally arrived at the southern coast of Norway, they spent the next three weeks imaging herring, cod, and capelin along the entire Norwegian coast, from the town of Alesund, north to the Russian border.</p>
<p>“The underwater terrain was as treacherous as the land, with submerged seamounts, ridges, and fjord channels,” Makris recalls. “Billions of herring actually would hide in one of these submerged fjords near Alesund during the daytime, about 300 meters down, and come up at night to shelves about 100 meters deep. Our mission there was to instantaneously image entire shoals of them, stretching for kilometers, and sort out their behavior.”</p>
<p><strong>A window through a hurricane</strong></p>
<p>As they moved up the Norwegian coast, the researchers towed a 0.5-kilometer-long array of passive underwater microphones and a device that emitted low-frequency sound waves. After imaging herring shoals in southern Norway, the team moved north to Lofoten, a dramatic archipelago of sheer cliffs and mountains, depicted most famously in Edgar Allen Poe’s “Descent into the Maelstrom,” in which the poet made note of the region’s abundance of cod.</p>
<p>To this day, Lofoten remains a primary spawning ground for cod, and there, Makris’ team was able to produce the first-ever images of an entire cod shoal, spanning 50 kilometers.</p>
<p>Toward the end of their journey, the researchers planned to image one last cod region, just as a hurricane was projected to hit. The team realized there would be only two windows of relatively calm winds in which to operate their imaging equipment.</p>
<p>“So we went, got good data, and fled to a nearby fjord as the eye wall struck,” Makris recalls. “We ended with 30-foot seas at dawn and the Norwegian coast guard, in a strangely soothing young voice, urging us to evacuate the area.” The team was able to image a slightly smaller shoal there, spanning about 10 kilometers, before completing the expedition.</p>
<p><strong>On the brink</strong></p>
<p>Back on dry land, the researchers analyzed their images and estimated that an average shoal size consists of about 10 million fish. They also looked at historical tallies of cod, in Norway, New England, the North Sea and Canada, and discovered an interesting trend: Those regions — like New England &nbsp;— that experienced long-lasting declines in cod stocks did so when the total cod population dropped below roughly 10 million — the same number as an average shoal. When cod dropped below this threshold, the population took decades to recover, if it did at all.</p>
<p>In Norway, the cod population always stayed above 10 million and was able to recover, climbing back to preindustrial levels over the years, even after significant declines in the mid-20th century. The team also imaged shoals of herring &nbsp;and found a similar trend through history: When the total population dropped below the level of an average herring spawning shoal, it took decades for the fish to recover.</p>
<p>Makris and Godø hope that the team’s results will serve as a measuring stick of sorts, to help researchers keep track of fish stocks and recognize when a species is on the brink.</p>
<p>“The ocean is a dark place, you look out there and can’t see what’s going on,” Makris says. “It’s a free-for-all out there, until you start shining a light on it and seeing what’s happening. Then you can properly appreciate and understand and manage.” He adds “Even if field work is difficult, time consuming, and expensive, it is essential to confirm and inspire theories, models, and simulations.”</p>
<p>This research was supported, in part, by the Norwegian Institute of Marine Research, the Office of Naval Research, and the National Science Foundation.</p>
The RV Knorr, in Norway’s Alesund harbor in February 2014, as the crew prepares to begin its Nordic Seas Experiment.Image: Michael Collins, U.S. Naval Research LaboratoryEnvironment, Mechanical engineering, Oceanography and ocean engineering, Research, School of Engineering, National Science Foundation (NSF)Arctic ice sets speed limit for major ocean currenthttps://news.mit.edu/2018/arctic-ice-sets-speed-ocean-current-1017
Long-term melting may lead to release of huge volumes of cold, fresh water into the North Atlantic, impacting global climate.Wed, 17 Oct 2018 00:00:00 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2018/arctic-ice-sets-speed-ocean-current-1017<p>The Beaufort Gyre is an enormous, 600-mile-wide pool of swirling cold, fresh water in the Arctic Ocean, just north of Alaska and Canada. In the winter, this current is covered by a thick cap of ice. Each summer, as the ice melts away, the exposed gyre gathers up sea ice and river runoff, and draws it down to create a huge reservoir of frigid fresh water, equal to the volume of all the Great Lakes combined.</p>
<p>Scientists at MIT have now identified a key mechanism, which they call the “ice-ocean governor,” that controls how fast the Beaufort Gyre spins and how much fresh water it stores. In a paper published today in <em>Geophysical Research Letters</em>, the researchers report that the Arctic’s ice cover essentially sets a speed limit on the gyre’s spin.</p>
<p>In the past two decades, as temperatures have risen globally, the Arctic’s summer ice has progressively shrunk in size. The team has observed that, with less ice available to control the Beaufort Gyre’s spin, the current has sped up in recent years, gathering up more sea ice and expanding in both volume and depth.</p>
<p>If global temperatures continue to climb, the researchers expect that the mechanism governing the gyre’s spin will diminish. With no governor to limit its speed, the researchers say the gyre will likely transition into “a new regime” and eventually spill over, like an overflowing bathtub, releasing huge volumes of cold, fresh water into the North Atlantic, which could affect the global climate and ocean circulation.</p>
<p>“This changing ice cover in the Arctic is changing the system which is driving the Beaufort Gyre, and changing its stability and intensity,” says Gianluca Meneghello, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “If all this fresh water is released, it will affect the circulation of the Atlantic.”</p>
<p>Meneghello is a co-author of the paper, along with John Marshall, the Cecil and Ida Green Professor of Oceanography, Jean-Michel Campin and Edward Doddridge of MIT, and Mary-Louise Timmermans of Yale University.</p>
<p><strong>A “new Arctic ocean”</strong></p>
<p>There have been a handful of times in the recorded past when the Beaufort Gyre has spilled over, beginning with the Great Salinity Anomaly in the late 1960s, when the gyre sent a surge of cold, fresh water southward. Fresh water has the potential to dampen the ocean’s overturning circulation, affecting surface temperatures and perhaps storminess and climate.</p>
<p>Similar events could transpire if the Arctic ice controlling the Beaufort Gyre’s spin continues to recede each year.</p>
<p>“If this ice-ocean governor goes away, then we will end up with basically a new Arctic ocean,” Marshall says.</p>
<p><strong>“Nature has a natural governor”</strong></p>
<p>The researchers began looking into the dynamics of the Beaufort Gyre several years ago. At that time, they used measurements taken by satellites between 2003 and 2014, to track the movement of the Arctic ice cover, along with the speed of the Arctic wind. They used these measurements of ice and wind speed to estimate how fast the Beaufort Gyre must be downwelling, or spinning down beneath the ice. But the number they came up with was much smaller than what they expected.</p>
<p>“We thought there was a coding error,” Marshall recalls. “But it turns out there was something else kicking back.” In other words, there must be some other mechanism that was limiting, or slowing down, the gyre’s spin.</p>
<p>The team recalculated the gyre’s speed, this time by including estimates of ocean current activity in and around the gyre, which they inferred from satellite measurements of sea surface heights. The new estimate, Meneghello says, was “much more reasonable.”</p>
<p>In this new paper, the researchers studied the interplay of ice, wind, and ocean currents in more depth, using a high-resolution, idealized representation of ocean circulation based on the MIT General Circulation Model, built by Marshall’s group. They used this model to simulate the seasonal activity of the Beaufort Gyre as the Arctic ice expands and recedes each year.</p>
<p>They found that in the spring, as the Arctic ice melts away, the gyre is exposed to the wind, which acts to whip up the ocean current, causing it to spin faster and draw down more fresh water from the Arctic’s river runoff and melting ice. In the winter, as the Arctic ice sheet expands, the ice acts as a lid, shielding the gyre from the fast-moving winds. As a result, the gyre spins against the underside of the ice and eventually slows down.</p>
<p>“The ice moves much slower than wind, and when the gyre reaches the velocity of the ice, at this point, there is no friction — they’re rotating together, and there’s nothing applying a stress [to speed up the gyre],” Meneghello says. “This is the mechanism that governs the gyre’s speed.”</p>
<p>“In mechanical systems, the governor, or limiter, kicks in when things are going too fast,” Marshall adds. “We found nature has a natural governor in the Arctic.”</p>
<p><img alt="" src="/sites/mit.edu.newsoffice/files/images/beaufort-gyre-3.gif" style="width: 500px; height: 417px;" /></p>
<p><em><span style="font-size:10px;">The evolution of sea ice over the Beaufort Gyre: In springtime, as ice thaws and melts into the sea, the gyre is exposed to the Arctic winds. Courtesy of the researchers</span></em></p>
<p><strong>“In a warming world”</strong></p>
<p>Marshall and Meneghello note that, as Arctic temperatures have risen in the last two decades, and summertime ice has shrunk with each year, the speed of the Beaufort Gyre has increased. Its currents have become more variable and unpredictable, and are only slightly slowed by the return of ice in the winter.</p>
<p>“At some point, if this trend continues, the gyre can’t swallow all this fresh water that it’s drawing down,” Marshall says. Eventually, the levee will likely break and the gyre will burst, releasing hundreds of billions of gallons of cold, fresh water into the North Atlantic.</p>
<p>An increasingly unstable Beaufort Gyre could also disrupt the Arctic’s halocline — the layer of ocean water underlying the gyre’s cold freshwater, that insulates it from much deeper, warmer, and saltier water. If the halocline is somehow weakened by a more instable gyre, this could encourage warmer waters to rise up, further melting the Arctic ice.</p>
<p>“This is part of what we’re seeing in a warming world,” Marshall says. “We know the global mean temperatures are going up, but the Arctic tempertures are going up even more. So the Arctic is very vulnerable to climate change. And we’re going to live through a period where the governor goes away, essentially.”</p>
<p>This research was supported, in part, by the National Science Foundation.</p>
A large pool of meltwater over sea ice in the Beaufort SeaNASA/Operation IceBridgeClimate, Climate change, EAPS, Earth and atmospheric sciences, Environment, Fluid dynamics, Global Warming, Oceanography and ocean engineering, Ocean science, Research, Satellites, School of Science, National Science Foundation (NSF)Technique quickly identifies extreme event statisticshttps://news.mit.edu/2018/offshore-risk%20assessment-identifies-extreme-event-1015
Machine-learning model provides risk assessment for complex nonlinear systems, including boats and offshore platforms.Mon, 15 Oct 2018 15:03:46 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2018/offshore-risk%20assessment-identifies-extreme-event-1015<p>Seafaring vessels and offshore platforms endure a constant battery of waves and currents. Over decades of operation, these structures can, without warning, meet head-on with a rogue wave, freak storm, or some other extreme event, with potentially damaging consequences.</p>
<p>Now engineers at MIT have developed an algorithm that quickly pinpoints the types of extreme events that are likely to occur in a complex system, such as an ocean environment, where waves of varying magnitudes, lengths, and heights can create stress and pressure on a ship or offshore platform. The researchers can simulate the forces and stresses that extreme events — in the form of waves — may generate on a particular structure.</p>
<p>Compared with traditional methods, the team’s technique provides a much faster, more accurate risk assessment for systems that are likely to endure an extreme event at some point during their expected lifetime, by taking into account not only the statistical nature of the phenomenon but also the underlying dynamics.</p>
<p>“With our approach, you can assess, from the preliminary design phase, how a structure will behave not to one wave but to the overall collection or family of waves that can hit this structure,” says Themistoklis Sapsis, associate professor of mechanical and ocean engineering at MIT. “You can better design your structure so that you don’t have structural problems or stresses that surpass a certain limit.”</p>
<p>Sapsis says that the technique is not limited to ships and ocean platforms, but can be applied to any complex system that is vulnerable to extreme events. For instance, the method may be used to identify the type of storms that can generate severe flooding in a city, and where that flooding may occur. It could also be used to estimate the types of electrical overloads that could cause blackouts, and where those blackouts would occur throughout a city’s power grid.</p>
<p>Sapsis and Mustafa Mohamad, a former graduate student in Sapsis’ group, currently assistant research scientist at Courant Institute of Mathematical Sciences at New York University, are publishing their results this week in the <em>Proceedings of the National Academy of Sciences</em>.</p>
<p><strong>Bypassing a shortcut</strong></p>
<p>Engineers typically gauge a structure’s endurance to extreme events by using computationally intensive simulations to model a structure’s response to, for instance, a wave coming from a particular direction, with a certain height, length, and speed. These simulations are highly complex, as they model not just the wave of interest but also its interaction with the structure. By simulating the entire “wave field” as a particular wave rolls in, engineers can then estimate how a structure might be rocked and pushed by a particular wave, and what resulting forces and stresses may cause damage.</p>
<p>These risk assessment simulations are incredibly precise and in an ideal situation might predict how a structure would react to every single possible wave type, whether extreme or not. But such precision would require engineers to simulate millions of waves, with different parameters such as height and length scale — a process that could take months to compute.&nbsp;</p>
<p>“That’s an insanely expensive problem,” Sapsis says. “To simulate one possible wave that can occur over 100 seconds, it takes a modern graphic processor unit, which is very fast, about 24 hours. We’re interested to understand what is the probability of an extreme event over 100 years.”</p>
<p>As a more practical shortcut, engineers use these simulators to run just a few scenarios, choosing to simulate several random wave types that they think might cause maximum damage. If a structural design survives these extreme, randomly generated waves, engineers assume the design will stand up against similar extreme events in the ocean.</p>
<p>But in choosing random waves to simulate, Sapsis says, engineers may miss other less obvious scenarios, such as combinations of medium-sized waves, or a wave with a certain slope that could develop into a damaging extreme event.</p>
<p>“What we have managed to do is to abandon this random sampling logic,” Sapsis says.</p>
<p><strong>A fast learner</strong></p>
<p>Instead of running millions of waves or even several randomly chosen waves through a computationally intensive simulation, Sapsis and Mohamad developed a machine-learning algorithm to first quickly identify the “most important” or “most informative” wave to run through such a simulation.</p>
<p>The algorithm is based on the idea that each wave has a certain probability of contributing to an extreme event on the structure. The probability itself has some uncertainty, or error, since it represents the effect of a complex dynamical system. Moreover, some waves are more certain to contribute to an extreme event over others.</p>
<p>The researchers designed the algorithm so that they can quickly feed in various types of waves and their physical properties, along with their known effects on a theoretical offshore platform. From the known waves that the researchers plug into the algorithm, it can essentially “learn” and make a rough estimate of how the platform will behave in response to any unknown wave. Through this machine-learning step, the algorithm learns how the offshore structure behaves over all possible waves. It then identifies a particular wave that maximally reduces the error of the probability for extreme events. This wave has a high probability of occuring and leads to an extreme event. In this way the algorithm goes beyond a purely statistical approach and takes into account the dynamical behavior of the system under consideration.</p>
<p>The researchers tested the algorithm on a theoretical scenario involving a simplified offshore platform subjected to incoming waves. The team started out by plugging four typical waves into the machine-learning algorithm, including the waves’ known effects on an offshore platform. From this, the algorithm quickly identified the dimensions of a new wave that has a high probability of occurring, and it maximally reduces the error for the probability of an extreme event.</p>
<p>The team then plugged this wave into a more computationally intensive, open-source simulation to model the response of a simplified offshore platform. They fed the results of this first simulation back into their algorithm to identify the next best wave to simulate, and repeated the entire process. In total, the group ran 16 simulations over several days to model a platform’s behavior under various extreme events. In comparison, the researchers carried out simulations using a more conventional method, in which they blindly simulated as many waves as possible, and were able to generate similar statistical results only after running thousands of scenarios over several months.</p>
<p><img alt="" src="/sites/mit.edu.newsoffice/files/images/ocean-event.gif" style="width: 400px; height: 225px;" /></p>
<p><span style="font-size:10px;"><em>MIT researchers simulated the behavior of a simplified offshore platform in response to the waves that are most likely to contribute to an extreme event.&nbsp;Courtesy of the researchers</em></span></p>
<p>Sapsis says the results demonstrate that the team’s method quickly hones in on the waves that are most certain to be involved in an extreme event, and provides designers with more informed, realistic scenarios to simulate, in order to test the endurance of not just offshore platforms, but also power grids and flood-prone regions.</p>
<p>“This method paves the way to perform risk assessment, design, and optimization of complex systems based on extreme events statistics, which is something that has not been considered or done before without severe simplifications,” Sapsis says. “We’re now in a position where we can say, using ideas like this, you can understand and optimize your system, according to risk criteria to extreme events.”</p>
<p>This research was supported, in part, by the Office of Naval Research, Army Research Office, and Air Force Office of Scientific Research, and was initiated through a grant from the American Bureau of Shipping.</p>
New research by MIT scientists may help engineers design more resilient offshore platforms.Courtesy of the researchersAlgorithms, Fluid dynamics, Machine learning, Mechanical engineering, Oceanography and ocean engineering, Research, School of Engineering, Water, WeatherFive from MIT earn Simons Foundation Postdoctoral Fellowships in Marine Microbial Ecologyhttps://news.mit.edu/2018/five-mit-whoi-and-cee-earn-simons-foundation-postdoctoral-fellowships-marine-microbial-ecology-1009
Awards emphasize cross-disciplinary training, support research to measure and model microbial communities and their influence on ocean processes.Tue, 09 Oct 2018 12:45:01 -0400EAPShttps://news.mit.edu/2018/five-mit-whoi-and-cee-earn-simons-foundation-postdoctoral-fellowships-marine-microbial-ecology-1009<p>Four current and former MIT-Woods Hole Oceanographic Institution Joint Program students (MIT-WHOI) and one postdoc from the Department of Civil and Environmental Engineering (CEE) have been awarded Simons Foundation Postdoctoral Fellowships in Marine Microbial Ecology, bringing the total of MIT awardees to five out of the nine fellowships granted nationally in 2018.</p>
<p>The Simons Foundation exists to advance the frontiers of research in mathematics and the basic sciences. Its Life Sciences division supports basic research on fundamental questions in biology, and is currently focused on origins of life, microbial oceanography, microbial ecology and evolution, and support of early career scientists. For the postdoctoral fellowships in marine microbial ecology, the foundation encourages applicants outside of strictly ocean research, seeking researchers interested in using cross-disciplinary experience, modeling, and theory development to explore the interrelationship of microorganisms and ocean processes.</p>
<p>“Postdoctoral fellows bring new ideas and energy to a field, so support for postdocs not only helps launch their careers but also pushes the field forward,” says&nbsp;Marian Carlson, director of life sciences at the foundation.</p>
<p>The awards are for three years and include an annual stipend and $25,000 towards research support.</p>
<p><strong>B.B. Cael</strong></p>
<p>MIT-WHOI Joint Program graduate student <a href="http://cael.space/">B.B. Cael</a> — currently working with Professor Mick Follows of the Department of Earth, Atmospheric and Planetary Sciences at MIT — successfully sought Simons Foundation support for a postdoctoral fellowship to build upon his thesis research on the export of biogenic carbon out of the surface ocean and attenuation of sinking particulate matter (SPM) through the ocean’s interior.</p>
<p>“Phytoplankton living in the sunlit surface ocean mediate the transformation of energy, carbon, and inorganic nutrients within the global marine biosphere,” Cael explains. “In the open ocean, the fraction of SPM that is not ‘remineralized’ or degraded by microbes in the photosynthetic zone becomes sequestered well below the permanent thermocline and is effectively removed from exchange with the atmosphere for decades to millennia. This process is one of many ways in which ocean ecology plays a role in our planet’s climate.”</p>
<p>As a postdoc with Angelique E. White in the Department of Oceanography at the University of Hawai’i, Cael will collect measurements to develop and test plausible and mechanistic theories for SPM flux that might provide an improved understanding for climate and ocean models.</p>
<p>Cael holds a BA in mathematics, human biology, and philosophy, and an MS in applied mathematics, both from Brown University.</p>
<p><strong>Matti Gralka</strong></p>
<p>MIT CEE postdoc <a href="https://sites.google.com/view/mattigralka/home" target="_blank">Matti Gralka</a> studies microscopic interactions in complex microbial communities on chitin particles in the lab of Otto Cordero, the Doherty Assistant Professor in Ocean Utilization and assistant professor of civil and environmental engineering at MIT. He plans to use the Simons award to investigate the resistance and resilience of marine microbial communities to perturbations.</p>
<p>“I am a physicist broadly interested in applying quantitative experiments and models towards understanding fundamental principles about biological systems and processes,” says Gralka. “At MIT, I will study the interplay of ecology and evolution, i.e., can we predict the assembly and function of microbial communities, their adaptation and response to perturbations, without a full knowledge of all microscopic details?”</p>
<p>Prior to MIT, Gralka completed his PhD in physics at the University of California at Berkeley working with Professor Oskar Hallatschek to study evolutionary dynamics in microbial colonies, investigating how spatial structure affects the action of selection.</p>
<p><strong>Bennett Lambert</strong></p>
<p>With this award from the Simons Foundation, graduate student <a href="https://www.bennettlambert.com/">Bennett Lambert</a> of CEE and the MIT-WHOI Joint Program will be pursuing his postdoctoral fellowship at the University of Washington, working with E. Virginia Armbrust on the behavior of marine microbes and the role diversity plays in survival.</p>
<p>Lambert’s current research in CEE Visiting Associate Professor Roman Stocker’s lab investigates the interactions of individual microbes and how those interactions scale up to affect biogeochemistry in the oceans. Traditional oceanographic techniques cannot be used to investigate the microorganisms, causing Lambert and his colleagues to engineer an in situ chemotaxis assay (ISCA). This allows the investigation of microbial behavior in their natural environment.</p>
<p>“To examine the interactions, I've been working to develop microfluidic techniques that can be applied in both the field and the lab. In the Armbrust Lab, I'll be continuing in the same vein and applying microfluidic techniques to study phenotypic heterogeneity in marine picoeukaryotes,” says Lambert.</p>
<p>Prior to MIT, Lambert completed his BS in civil and environmental engineering at the University of Alberta.</p>
<p>Also receiving 2018 Simons Foundation fellowships in marine microbial ecology are two alumni of the MIT-WHOI Joint Program: Emily Zakem PhD ’17 and Nicholas&nbsp;Hawko&nbsp;PhD ’17. Zakem, herself a former member of the Follows Group at MIT, will explore, “what controls the transition from aerobic to anaerobic microbial activity in the ocean,” in the laboratory of Professor Naomi Levine at the University of Southern California. Also at the University of Southern California, Hawko will be working on, “regional versus phylogenetic inheritance of iron metabolic traits in&nbsp;Prochlorococcus,” with Professor Seth John.</p>
<p>A complete <a href="https://www.simonsfoundation.org/grant/simons-postdoctoral-fellowships-in-marine-microbial-ecology/?tab=awardees" target="_blank">list of the award recipients and their projects</a>&nbsp;is available at the Simons Foundation website.</p>
Marine bacteria form a community on a nutrient particle in the Cordero Lab.Image: Julien Barrere/Cordero Lab at MITAwards, honors and fellowships, EAPS, Woods Hole, Civil and environmental engineering, Students, Graduate, postdoctoral, Oceanography and ocean engineering, Biology, Marine biology, School of Science, School of EngineeringBeach sand ripples can be fingerprints for ancient weather conditionshttps://news.mit.edu/2018/beach-sand-ripples-ancient-weather-0928
Experiments show shifting ripple patterns can signal times of environmental flux.Thu, 27 Sep 2018 23:59:59 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2018/beach-sand-ripples-ancient-weather-0928<p>When a coastal tide rolls out, it can reveal beautiful ripples in the temporarily exposed sand. These same undulating patterns can also be seen in ancient, petrified seabeds that have been exposed in various parts of the world and preserved for millions or even billions of years.</p>
<p>Geologists look to ancient sand ripples for clues to the environmental conditions in which they formed. For instance, the spacing between ripples is proportional to the depth of the water and the size of the waves that molded the underlying ripples.</p>
<p>But sand ripples aren’t always perfectly parallel, carbon-copies of each other, and can display various kinks and sworls. Can these more subtle, seemingly random deviations or defects tell us something about the conditions in which a sandy seabed formed?</p>
<p>The answer, according to researchers from MIT and elsewhere, is yes. In a paper published online and appearing in the Oct. 1 issue of <em>Geology</em>, the team reports that some common defects found in both ancient and modern seabeds are associated with certain wave conditions. In particular, their findings suggest that ripple defects resembling hourglasses, zigzags, and tuning forks were likely shaped in periods of environmental flux — for instance, during strong storms, or significant changes in tidal flows.</p>
<p>“The type of defect you see in ripples could tell you about how dramatic the shifts in weather conditions were at the time,” says Taylor Perron, associate professor of geology and associate head of MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “We can use these defects as fingerprints to tell not just what the average conditions were in the past, but how things were changing.”</p>
<p>Ripple defects in ancient sandbeds may also influence how fluids flow through sedimentary rocks, including underground reservoirs that hold water, oil and gas, or even stored carbon dioxide, according to Perron.</p>
<p>In addition, he says, ripple patterns in modern sand act to roughen the seabed, slowing down ocean currents near the shore. Knowing how ripples change in response to shifting waves and tides may therefore help predict coastal erosion and flooding.</p>
<p>Perron’s co-authors are on the paper are former MIT graduate student Kimberly Huppert ’11, PhD ’17, former undergraduate and current postdoc Abigail Koss ’12, Paul Myrow of Colorado College, and former undergraduate Andrew Wickert ’08 of the University of Minnesota.</p>
<div class="cms-placeholder-content-video"></div>
<p><strong>Wrinkles preserved</strong></p>
<p>The team began looking into the significance of ripple defects several years ago, when Myrow, who at the time was spending his sabbatical at MIT, showed Perron some photos that he had taken of sedimentary rocks etched with ripples and grooves. The rocks were, in fact, ancient sandbeds that were hundreds of millions of years old.</p>
<p>Wave-sculpted ripples form as waves travel across the surface of a body of liquid. These waves cause water beneath the surface to circle around and around, generating oscillating flows that pick up sand grains and set them down in a process that eventually carves out troughs and grooves throughout the sandbed.</p>
<p>But how could such delicate patterns be preserved for millions of years? Perron says that various processes could essentially set ripples in place. For instance, if the water level suddenly dropped, it could leave a sand bed’s ripples exposed to the air, drying them out and hardening them to some extent, so that they retained their patterns even as more sediment slowly layered itself on top of them over billions of years.</p>
<p>Similarly, if a finer sediment like mud or silt covers a sand bed, such as after a large storm, these sediments could blanket the existing ripples. As Perron explains, this would essentially “armor them, keeping the waves from eroding the ripples before more sediment buries them.” Over time, the sediments turn into rock as they are buried deep below Earth’s surface. Later, the rock overlaying the ripples can naturally erode away, exposing the preserved ripples at the surface again.</p>
<p>In looking through photos of sand ripples, Perron and Myrow noticed small defects resembling tuning forks, zigzags, and hourglasses, across both ancient and modern sandbeds.</p>
<p>“People have noticed these defects before, but we wondered, are they just random, or do they actually contain some information?” Perron says.</p>
<p><strong>Paddling through waves</strong></p>
<p>The researchers set out to study the various wave conditions that generate certain ripple patterns and defects. To do this, they built an acrylic wave tank measuring 60 centimers wide, 50 centimers deep, and 7 meters long. At one end of the tank, they attached a motor-driven paddle, which swished back and forth to generate waves that traveled across the tank.</p>
<p>At the other end of the tank, they erected an artificial sloping “beach” covered in a polymer mesh. This setup served to minimize any wave reflections: As a wave crashed onto the artificial beach, the energy dissipated within the mesh instead of splashing back and influencing oncoming waves.</p>
<p>The team filled the tank with a 5-centimeter-thick bed of fine sand and enough water to reach 40 centimeters in depth. For each experiment, they set the paddle to swish back and forth at a constant distance, and recorded the sand bed as ripples formed. At a certain point, they observed that the ripples — and in particular, the spacing between the ripples — reaches a stable, consistent pattern. They recorded this spacing, along with the speed and amplitude of the paddle, and then, over 32 experimental runs, either increased or decreased the paddle’s motion, causing the ripples to morph again to either a wider or narrower spacing.</p>
<p>Interestingly, they found that, in the process of adjusting to a new spacing, ripples formed intermediary defects resembling zigzags, hourglasses, and tuning forks, depending on the wave conditions set by the tank’s paddle.</p>
<p>As the researchers shortened the paddle’s back-and-forth motion, this created shorter waves, narrower ripples, and patterns that resembled hourglasses. If the paddle’s motion was shortened even further — creating faster, shorter waves — a pattern of “secondary crests,” in which existing ripples appeared to form temporary “shadow” ripples on either side, took over. When the researchers widened the paddle’s motion, generating longer waves, the ripples formed zigzag patterns as they shifted to a wider spacing.</p>
<p>“If you see these types of defects in nature, we argue that the seabed was undergoing some kind of change in weather conditions, tides, or something else that affected water depth or waves, probably over the course of hours or days,” Perron says. “For instance, if you’re seeing lots of secondary crests, you can tell there was a pretty big change in the waves as opposed to a smaller change, which might give you hourglasses instead.”</p>
<p>The researchers observed that in all scenarios, patterns resembling tuning forks cropped up, even after ripples had reached a new, stable spacing.</p>
<p>“These tuning forks tend to stick around for a long time,” Perron says. “If you see these in modern or ancient rock, they suggest a seabed experienced a change, but then the conditions remained steady, and the bed had a long time to adjust.”</p>
<p>Going forward, Perron says geologists can use the team’s results as a blueprint to connect certain ripple defects with the water conditions that may have created them, in both the modern environment and in the ancient past. &nbsp;</p>
<p>“We think these small defects can tell you a lot more about an ancient environment than just what the average size of the waves and water depth was,” Perron says. “They could tell you if it was an environment that had tides that were large enough to change ripples by this much, or if a place was experiencing periodic storms, even billions of years ago. And if we find ancient wave ripples on Mars, we’ll know how to read them.”</p>
<p>This research was supported, in part, by the National Science Foundation.</p>
MIT researchers have found that patterns of ripples created in sand, and preserved for thousands to millions of years, can reveal clues to ancient environments. Image courtesy of the researchersEAPS, Earth and atmospheric sciences, Environment, Fluid dynamics, Geology, Research, School of Science, Water, Oceanography and ocean engineeringAdvancing undersea optical communicationshttps://news.mit.edu/2018/advancing-undersea-optical-communications-0817
Lincoln Laboratory researchers are applying narrow-beam laser technology to enable communications between underwater vehicles. Fri, 17 Aug 2018 00:00:00 -0400Nathan Parde | Lincoln Laboratoryhttps://news.mit.edu/2018/advancing-undersea-optical-communications-0817<p>Nearly five years ago, NASA and Lincoln Laboratory made history when the Lunar Laser Communication Demonstration (LLCD) used a pulsed laser beam to transmit data from a satellite orbiting the moon to Earth — more than 239,000 miles — at a record-breaking download speed of 622 megabits per second.</p>
<p>Now, researchers at Lincoln Laboratory are aiming to once again break new ground by applying the laser beam technology used in LLCD to underwater communications.</p>
<p>“Both our undersea effort and LLCD take advantage of very narrow laser beams to deliver the necessary energy to the partner terminal for high-rate communication,” says Stephen Conrad, a staff member in the Control and Autonomous Systems Engineering Group, who developed the pointing, acquisition, and tracking (PAT) algorithm for LLCD. “In regard to using narrow-beam technology, there is a great deal of similarity between the undersea effort and LLCD.”</p>
<p>However, undersea laser communication (lasercom) presents its own set of challenges. In the ocean, laser beams are hampered by significant absorption and scattering, which restrict both the distance the beam can travel and the data signaling rate. To address these problems, the Laboratory is developing narrow-beam optical communications that use a beam from one underwater vehicle pointed precisely at the receive terminal of a second underwater vehicle.</p>
<p>This technique contrasts with the more common undersea communication approach that sends the transmit beam over a wide angle but reduces the achievable range and data rate. “By demonstrating that we can successfully acquire and track narrow optical beams between two mobile vehicles, we have taken an important step toward proving the feasibility of the laboratory’s approach to achieving undersea communication that is 10,000 times more efficient than other modern approaches,” says Scott Hamilton, leader of the Optical Communications Technology Group, which is directing this R&amp;D into undersea communication.</p>
<p>Most above-ground autonomous systems rely on the use of GPS for positioning and timing data; however, because GPS signals do not penetrate the surface of water, submerged vehicles must find other ways to obtain these important data. “Underwater vehicles rely on large, costly inertial navigation systems, which combine accelerometer, gyroscope, and compass data, as well as other data streams when available, to calculate position,” says Thomas Howe of the research team. “The position calculation is noise sensitive and can quickly accumulate errors of hundreds of meters when a vehicle is submerged for significant periods of time.”</p>
<p>This positional uncertainty can make it difficult for an undersea terminal to locate and establish a link with incoming narrow optical beams. For this reason, "We implemented an acquisition scanning function that is used to quickly translate the beam over the uncertain region so that the companion terminal is able to detect the beam and actively lock on to keep it centered on the lasercom terminal’s acquisition and communications detector," researcher Nicolas Hardy explains. Using this methodology, two vehicles can locate, track, and effectively establish a link, despite the independent movement of each vehicle underwater.</p>
<p>Once the two lasercom terminals have locked onto each other and are communicating, the relative position between the two vehicles can be determined very precisely by using wide bandwidth signaling features in the communications waveform. With this method, the relative bearing and range between vehicles can be known precisely, to within a few centimeters, explains Howe, who worked on the undersea vehicles’ controls.</p>
<p>To test their underwater optical communications capability, six members of the team recently completed a demonstration of precision beam pointing and fast acquisition between two moving vehicles in the Boston Sports Club pool in Lexington, Massachusetts. Their tests proved that two underwater vehicles could search for and locate each other in the pool within one second. Once linked, the vehicles could potentially use their established link to transmit hundreds of gigabytes of data in one session.</p>
<p>This summer, the team is traveling to regional field sites to demonstrate this new optical communications capability to U.S. Navy stakeholders. One demonstration will involve underwater communications between two vehicles in an ocean environment — similar to prior testing that the Laboratory undertook at the Naval Undersea Warfare Center in Newport, Rhode Island, in 2016. The team is planning a second exercise to demonstrate communications from above the surface of the water to an underwater vehicle — a proposition that has previously proven to be nearly impossible.</p>
<p>The undersea communication effort could tap into innovative work conducted by other groups at the laboratory. For example, integrated blue-green optoelectronic technologies, including gallium nitride laser arrays and silicon Geiger-mode avalanche photodiode array technologies, could lead to lower size, weight, and power terminal implementation and enhanced communication functionality.<br />
<br />
In addition, the ability to move data at megabit-to gigabit-per-second transfer rates over distances that vary from tens of meters in turbid waters to hundreds of meters in clear ocean waters will enable undersea system applications that the laboratory is exploring.</p>
<p>Howe, who has done a significant amount of work with underwater vehicles, both before and after coming to the laboratory, says the team’s work could transform undersea communications and operations. “High-rate, reliable communications could completely change underwater vehicle operations and take a lot of the uncertainty and stress out of the current operation methods."</p>
A remotely operated vehicle and undersea terminal emits a coarse acquisition stabilized beam after locking onto another lasercom terminal.Photo: Nicole FandelResearch, Lincoln Laboratory, Oceanography and ocean engineering, Lasers, Communications, optoelectronicsCollaboration to expand the study of microbial oceanographyhttps://news.mit.edu/2018/simons-collaboration-expand-study-of-microbial-oceanography-cbiomes-0710
Simons Foundation-backed CBIOMES brings together researchers in oceanography, statistics, data science, ecology, biogeochemistry, and remote sensing.Tue, 10 Jul 2018 17:20:01 -0400Helen Hill | EAPShttps://news.mit.edu/2018/simons-collaboration-expand-study-of-microbial-oceanography-cbiomes-0710<p>Microbes sustain all of Earth’s habitats, including its largest biome, the global ocean. Microbes in the sea capture solar energy, catalyze biogeochemical transformations of important elements, produce and consume greenhouse gases, and fuel the marine food web. Measuring and modeling the distribution, composition, and function of microbial communities, and their interactions with the environment, are key to understanding these fundamental processes in the ocean.</p>
<p>The Simons Foundation, which provides generous funding for several lines of research within MIT's Department of Earth, Atmospheric and Planetary Sciences, recently extended its support for microbial oceanography with the establishment of the Simons Foundation Collaboration on Ocean Computational Biogeochemical Modeling of Marine Ecosystems (CBIOMES). Led by MIT professor of oceanography&nbsp;<a href="http://eapsweb.mit.edu/people/mick" target="_blank">Michael Follows</a>, CBIOMES draws together an multidisciplinary group of both U.S. and international investigators bridging oceanography, statistics, data science, ecology, biogeochemistry, and remote sensing.</p>
<p>The goal of CBIOMES (pronounced “sea biomes”), which leverages and extends Follow’s <a href="http://darwinproject.mit.edu/" target="_blank">Darwin Project</a> activity, is to develop and apply quantitative models of the structure and function of marine microbial communities at seasonal and basin scales.</p>
<p>As Follows explains, “Microbial communities in the sea mediate the global cycles of elements including climatically significant carbon, sulfur and nitrogen. Photosynthetic microbes in the surface ocean fix these elements into organic molecules, fueling food webs that sustain fisheries and most other life in the ocean. Sinking and subducted organic matter is remineralized and respired in the dark, sub-surface ocean, maintaining a store of carbon about three times the size of the atmospheric inventory of CO<sub>2</sub>.”</p>
<p>The communities of microbes that sustain these global-scale cycles are functionally and genetically extremely diverse, non-uniformly distributed and sparsely sampled. Their biogeography reflects selection according to the relative fitness of myriad combinations of traits that govern interactions with the environment and other organisms. Trait-based theory and simulations provide tools with which to interpret biogeography and microbial mediation of biogeochemical cycles. Follows says, “Several outstanding challenges remain: Observations to constrain the biogeography of marine microbes are still sparse and based on eclectic sampling methods. Theories of the organization of the system have not been quantitatively tested, and the models used to simulate the system still lack sufficiently mechanistic biological foundations. Addressing these issues will enable meaningful, dynamic simulations and state estimation.”</p>
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<p>CBIOMES seeks to integrate key new data sets in real-time as they are collected at sea to facilitate direct tests of theoretical predictions to synthesize an atlas of marine microbial biogeography suitable for testing a range of specific ecological theories and quantifying the skill of numerical simulations. It also aspires to develop new trait-based models and simulations of regional and global microbial communities bringing to bear the power of metabolic constraints and knowledge of macro-molecular composition; to analyze these data and models using statistical tools to interpolate and extrapolate the sparse data sets, formally quantify the skill of numerical simulations, and employ data assimilation technologies to identify and optimize compatible model frameworks. “Together, the results of these efforts will advance new theoretical approaches and lead to improved global ocean-scale predictions and regional state-estimates, constrained by observed biogeography. They will provide a quantification of the associated biogeochemical fluxes,” says Follows.</p>
<p>Working with Follows on CBIOMES are principal investigators <a href="http://eapsweb.mit.edu/people/stephdut" target="_blank">Stephanie Dutkiewicz</a> of MIT; <a href="http://www.simonsfoundation.org/team/jacob-bien/" target="_blank">Jacob Bien</a>,&nbsp;<a href="http://www.simonsfoundation.org/team/christopher-edwards/" target="_blank">Christopher Edwards</a>, and&nbsp;<a href="http://www.simonsfoundation.org/team/jed-fuhrman/" target="_blank">Jed Fuhrman</a> of the University of Southern California; <a href="http://www.simonsfoundation.org/team/zoe-finkel-2/" target="_blank">Zoe Finkel</a>&nbsp;and&nbsp;<a href="http://www.simonsfoundation.org/team/andrew-irwin/" target="_blank">Andrew Irwin</a> of Mount Allison University in Canada; <a href="http://www.simonsfoundation.org/team/shubha-sathyendranath/" target="_blank">Shubha Sathyendranath</a> of Plymouth Marine Laboratory in the U.K., and&nbsp;<a href="http://www.simonsfoundation.org/team/joseph-vallino/" target="_blank">Joseph Vallino</a> of the Marine Biological Laboratory.</p>
<p>A meeting held at the Simons Foundation in New York City May 21 through 23 provided a first opportunity for collaborators to meet face-to-face, and provided a forum for investigators to educate one another about each others expertise and areas of activity, share initial progress, and coordinate collaborative efforts.</p>
<p>Discussions centered around how to determine the biogeography of marine microbes from empirical date, the role of statistical models in determining the relationships in space and time between organisms, traits, and environments, the complimentary role of mechanistic models and how to simulate the systems that are observed, and, in the context of model-date synthesis, how to best utilize empirical data to test theory and improve simulation skill.</p>
<p>“While the central question 'What is the functional biogeography of a group of organisms in the oceans?' is relatively focused, the techniques being used are extremely varied focusing a lot on computational tools, but uniquely, hand-in-hand with data collection and data compilation,” says Follows. “I am particularly excited by everyone’s enthusiasm, the number of cross-connections and collaborations already underway, and the rapid progress that is happening on many fronts.”</p>
<p>Complementary to CBIOMES is the&nbsp;<a href="http://scope.soest.hawaii.edu/" target="_blank">Simons Collaboration on Ocean Processes and Ecology (SCOPE)</a>&nbsp;co-led by&nbsp;<a href="http://www.simonsfoundation.org/team/edward-f-delong/" target="_blank">Ed DeLong</a> of the MIT Department of Civil and Environmental Engineering and&nbsp;<a href="https://www.simonsfoundation.org/team/david-m-karl/" target="_blank">David Karl</a> of the University of Hawaii. SCOPE’s focus is advancing understanding of marine biology, biogeochemistry, ecology and evolution of microbial processes by focusing on a representative ocean benchmark, Station ALOHA, located in the North Pacific Subtropical Gyre.</p>
<p><a href="http://www.simonsfoundation.org/life-sciences/microbial-oceanography/simons-collaboration-on-ocean-processes-and-ecology-gradients/about-scope-gradients/" target="_blank">SCOPE-Gradients</a>, a related project, with a focus on understanding transitions between the North Pacific Subtropical Gyre and neighboring ecosystems, brings a rich stream of observational data to the CBIOMES effort. The North Pacific Subpolar Gyre is a region of open ocean notable for exhibiting steep changes in environmental conditions (gradients) associated with dramatic changes in the microbial ecosystem. Several members of the SCOPE-Gradients team accompanied project principal investigator <a href="http://www.simonsfoundation.org/team/e-virginia-armbrust/" target="_blank">Virginia Armbrust</a> of the University of Washington to the May CBIOMES meeting.</p>
<p>The mission of the Simons Foundation is to advance the frontiers of research in mathematics and the basic sciences. Co-founded in New York City by Jim and Marilyn Simons, the foundation exists to support basic — or discovery-driven — scientific research undertaken in the pursuit of understanding the phenomena of our world.</p>
<p>As well as&nbsp;Michael Follows, other Simons Foundation funded investigators in the MIT Department of Earth, Atmospheric and Planetary Sciences include&nbsp;<a href="http://eapsweb.mit.edu/people/tbosak" target="_blank">Tanja Bosak</a>,&nbsp;<a href="http://eapsweb.mit.edu/people/g4nier" target="_blank">Gregory Fournier</a>, and&nbsp;<a href="http://eapsweb.mit.edu/people/rsummons" target="_blank">Roger Summons</a>. Several MIT postdocs have been recipients of Simons Postdoctoral Fellowships, among them&nbsp;<a href="http://eapsweb.mit.edu/people/avjohns" target="_blank">Alexandria Johnson</a>,&nbsp;<a href="http://eapsweb.mit.edu/people/sukrit" target="_blank">Sukrit Ranjan</a>&nbsp;and&nbsp;<a href="http://eapsweb.mit.edu/people/follett" target="_blank">Christopher Follett</a>.</p>
A computer simulation shows ecological provinces of the marine global ecosystems developed in the Follows Group at MIT. Each color represents a different combination of the most dominant phytoplankton function types (as shown in the Venn diagram at top right). Opacity indicates the total concentration of phytoplankton biomass: The darker the color, the less phytoplankton.Image: Oliver Jahn / MIT EAPSOceanography and ocean engineering, Marine biology, Ecology, Earth and atmospheric sciences, EAPS, Data, Funding, Civil and environmental engineering, School of Science, School of Engineering, Biology, EvolutionTies with MIT run deep for the US Navy’s top officerhttps://news.mit.edu/2018/ties-with-mit-run-deep-us-navy-top-officer-admiral-john-richardson-0706
Chief of Naval Operations Admiral John Richardson SM ’89, EE ’89, ENG ’89 poses global challenges to academe.
Fri, 06 Jul 2018 14:05:30 -0400Meg Murphy | School of Engineeringhttps://news.mit.edu/2018/ties-with-mit-run-deep-us-navy-top-officer-admiral-john-richardson-0706<p>Looking back on his MIT graduate student days in the late 1980s, Admiral John M. Richardson SM ’89, EE ’89, ENG ’89 recalls a quieter time. He was not yet helming the world’s most powerful navy nor was global competition at sea nearly so high.</p>
<p>Richardson is now the chief of naval operations (CNO), the senior four-star admiral leading the U.S. Navy. This position places him on the Joint Chiefs of Staff as adviser to the secretary of defense and the president. He draws on his deep ties to academe to help the Navy keep pace.</p>
<p>From his graduate student days to today what has remained unchanged are the depth of his attachment to MIT and the warmth and respect between Richardson and his mentors in the MIT-Woods Hole Oceanographic Institution Joint Program.</p>
<p>“As a graduate student, John clearly stood out as brilliant, a leader, and wonderfully warm and friendly,” says Alan Oppenheim, an MIT Ford Professor of Engineering.</p>
<p>After his time at MIT and Woods Hole, Richardson went on to command the submarine USS Honolulu, a ship known in the Navy for the important missions for which it was tasked. Before that command he was posted at the White House as President Clinton’s Navy adviser. Just before being selected to be the CNO he was in charge of all of the nuclear reactor technology in the Navy.</p>
<p>“It is so striking that through his ascendancy in the Navy, John never lost these professional and personal qualities. He is as approachable today as he was back then,” Oppenheim says.</p>
<p><strong>The power of relationships</strong></p>
<p>Richardson recently took time from his schedule to articulate the significance of MIT in his life and career. He says friendships that began during graduate work quickly expanded to bluefish barbeques, bike riding, wind surfing, and listening to jazz and country music together, and many other things that “we still share even 30 years later.”</p>
<p>He speaks with affection of strong relationships with academics such as Oppenheim and Arthur Baggeroer, an MIT professor of mechanical, ocean, and electrical engineering and a Ford Professor of Engineering, Emeritus. “What I value most about my time at MIT are the enduring relationships with amazing people. Al, Art, and so many others have enriched my life so much — they are my mentors, my senseis.”</p>
<p>Richardson insists other alumni have made what he describes as “far<em> </em>more important contributions to the field of engineering.” And says for his part, he’s been able to apply his time at MIT to leading the Navy.</p>
<p>“In the end, it’s all about making our sailors the best in the world,” Richardson says. “The Navy that I'm so privileged to lead has always used world-leading technology, brought to life by our partnership with academe. MIT has always been a bright star in that constellation of innovation and excellence.”&nbsp;</p>
<p><strong>More like a family reunion</strong></p>
<p>Richardson recalls a fall 2017 symposium about the future of signal processing in honor of Oppenheim, a pioneer in the field. “I'll never forget the warm feelings of camaraderie that defined Al’s conference on the future of signal processing and 80th birthday celebration.” He describes himself as “super nervous” after accepting the invitation to speak because he knew “the world’s best would be there to listen.”</p>
<p>“All of that anxiety was instantly dispelled by the love and respect Al engenders in others, and that will always be part of his legacy. We all felt like family by our association with him and MIT,” Richardson says.</p>
<p>At the symposium, the admiral outlined the challenges ahead for the Navy and invited solutions. “I want to share with you my problems to provide a template for those of you all with solutions,” he said, standing in full dress uniform. “This is a continuation of a great tradition that we have between the Navy and MIT.”</p>
<p>The Navy faced a submarine problem in the Atlantic during World War II that MIT helped solve through a rigorous application of emerging science in operations research, he said. “Academe came to our rescue there.”</p>
<p>The same was true for the Battle of Britain, during which MIT-developed naval anti-aircraft technology played a pivotal role in beating back large-scale attacks by Nazi Germany. “We have a long tradition of working together.”</p>
<p>Among other things, MIT has a long-standing Graduate Program in Naval Construction and Marine Engineering in close cooperation with the Navy dating back to 1901. The <a href="http://web.mit.edu/2n/" target="_blank">2N program</a> combines cutting-edge technical initiatives with practical design and prepares U.S. Navy, U.S. Coast Guard, foreign naval officers, and other graduate students for careers in ships design and construction.</p>
<p><strong>Challenges in the maritime </strong></p>
<p>The traffic on the ocean has increased by a factor of four over the past 25 years, Richardson said to a packed room during the conference on the future of signal processing. “Just picture that curve in your mind. The amount of food we get from the sea has increased by more than a factor of 10 in the same time period.”</p>
<p>“The Arctic ice cap is the smallest it has been since we started taking measurements and getting smaller, and that has tremendous implications for traffic routes and access to resources,” he said.</p>
<p>The internet of things will include 30 billion devices connected by 2020. And 99 percent of web data rides on undersea cables on the sea floor. “It’s not about a cloud, it’s about the ocean,” said Richardson. “If cables are disturbed or disrupted, you can’t reconstitute that via satellites or anything else, you can only fight back and get about two percent.”</p>
<p>“Things are moving very quickly. It’s very competitive. We’ve done a lot of work to try and figure out — how should the Navy respond?” he said. Multiple analyses show a need for heightened naval capability. Yet even the most aggressive shipbuilding plan equates to reaching 350 ships in about 17 years.</p>
<p>In his presentation, Richardson pointed to a chart with icons representing the U.S. fleet: ships, satellites, submarines, and aircraft. Let’s redefine the axis, he said. The measure of naval capability no longer rests only on the numerical metric of physical things but also on the ability to network platforms and to manage information.</p>
<p>“Signal processing has a terrific and important role in helping us transcend just making more ships. We must make our ships – and our Navy – more capable as well,” said Richardson. He pointed to a new graph in which U.S. naval power rises beyond exponential curves as the fleet is deeply networked with the assistance of technologies such as artificial intelligence, human and machine teams, and quantum computing.</p>
<p><strong>Drawing on academe </strong></p>
<p>More recently, Richardson created Task Force Ocean, which seeks to link innovative research concepts with the needs of the U.S. Navy, especially undersea forces. The senior academic involved in these Navy efforts is Arthur Baggeroer.</p>
<p>“I have known every chief of naval operations over the last two decades, and John is by far the most engaged with academia,” says Baggeroer, who was the director of the MIT-WHOI program when Richardson enrolled in 1985. He also acted as academic advisor to Richardson and five additional naval officers in the program.</p>
<p>Over the years, Baggeroer kept up with Richardson as he rose through the ranks.</p>
<p>“He has been very supportive of the MIT-WHOI Joint Program and has taken steps to attract to the program younger officers with the same qualifications he had at the time,” adds Baggeroer.&nbsp;</p>
<p><strong>Setting a high bar</strong></p>
<p>Richardson was, by all accounts, a star graduate student. His career track and leadership continue to inspire Navy students, says Tim Stanton, scientist emeritus at the Woods Hole Oceanographic Institution. He joined Oppenheim as Richardson’s thesis advisor.</p>
<p>“Admiral Richardson sets the gold standard for excellence and leadership in the Navy,” says Stanton. “As I advised many Navy students for the nearly 30 years after Admiral Richardson graduated, they frequently referenced his leadership as a benchmark for their career goals. Through his leadership, he not only directly impacted Navy operations, but also the next generation of leaders in the Navy.”</p>
<p>“I’m so grateful for the continued friendship, partnership and leadership of MIT with the Navy,” says Richardson. “MIT has had an amazing impact on me and my life. It literally changed the way I think about things.”</p>
Chief of Naval Operations Admiral John Richardson SM ’89, EE ’89, ENG ’89 is the senior four-star admiral leading the U.S. Navy. He outlined the challenges ahead for the Navy and invited solutions during an MIT symposium in honor of one of his mentors, Alan Oppenheim, an MIT Ford Professor of Engineering. Photo: Gretchen ErtlAlumni/ae, Navy, Woods Hole, School of Engineering, Mechanical engineering, Oceanography and ocean engineering, Electrical Engineering & Computer Science (eecs)The race to build the Navy’s next fleet of shipshttps://news.mit.edu/2018/race-to-build-next-fleet-of-us-navy-ships-0628
Retired Rear Admiral Chuck Goddard OCE ’85, SM ’85 is leading a bid to design the US Navy’s next class of guided-missile frigates. Thu, 28 Jun 2018 17:00:01 -0400Mary Beth O'Leary | Department of Mechanical Engineeringhttps://news.mit.edu/2018/race-to-build-next-fleet-of-us-navy-ships-0628<p>Watching the USS<em> </em>Constitution sail around Boston Harbor is always a breathtaking sight. In June, spectators along the harbor got a particularly impressive display. The Constitution was joined on its cruise to Boston’s Fort Independence by the ITS<em> </em>Alpino<em>, </em>an Italian naval warship.</p>
<p>Fincantieri designed and built the ITS Alpino, and its Wisconsin company, Fincantieri Marinette Marine, has received a contract from the U.S. Navy, along with four other companies, to produce a conceptual design for the next generation of frigates — making the tour around Boston Harbor even more remarkable.<br />
<br />
“You had the oldest frigate in the Navy sailing alongside what will hopefully be the newest frigate in the Navy,” explains Chuck Goddard OCE ’85, SM ’85, retired Navy rear admiral and senior vice president of Fincantieri Marine Group.</p>
<p>A graduate of MIT’s naval architecture and marine engineering program, Goddard took the Alpino’s trip to Boston as an opportunity to reconnect with the MIT community. He invited faculty members Joe Harbour, professor of the practice of naval construction, and Nicholas Makris, professor of mechanical and ocean engineering and director of the Center for Ocean Engineering, along with a number of naval construction and engineering graduate students to take a guided tour of the ship.</p>
<p>“It was a great opportunity to show our students the finished product of a shipbuilding project,” says Harbour.</p>
<p>Goddard’s involvement in Fincantieri’s bid to design the Navy’s next fleet of frigates is the culmination of four-decades of designing and building ships. His career has straddled both the public and private sector, sent him from coast-to-coast, and placed him on dry land and the open ocean.</p>
<p>Goddard studied naval architecture at the United States Naval Academy in the late ’70s. After graduating and a stint in Pearl Harbor, Goddard became an engineering duty officer for the Navy. It was then he was given the opportunity to enroll in MIT’s naval architecture and marine engineering program (then known as Course 13A).</p>
<p>“When I showed up at MIT in June of ’82, I had been out at sea for three years,” recalls Goddard. “It was fun getting back into the academic world and spending that first summer getting up-to-speed on calculus and differential equations.”</p>
<p>During his time at MIT, Goddard was mentored by Captain Clark “Corky” Graham ME ’67, SM ’67, PhD ’69, a professor of naval construction and engineering. They worked together on figuring out how to incorporate electric drives in naval ships. Goddard also learned about basic ship design in a civilian ship design course taught by Chryssostomos Chryssostomidis, professor of mechanical engineering ocean engineering.</p>
<p>After graduating from MIT, it was time to get his feet wet once more in the Navy — quite literally. Goddard was sent to Panama City, Florida, where he became a qualified Navy hard-hat diver and salvage officer. “We were the ones doing the calculations for how to raise sunken ships,” he says. “It was a very fun summer.”</p>
<p>Goddard was then sent to Long Beach Naval Shipyard in California where he worked on putting the USS <em>Missouri</em> back in commission. As luck would have it, he was soon contacted by his old mentor, Corky Graham. “I got my wish come true working with Corky at the David Taylor Model Basin in Maryland,” Goddard recalls. “We worked on electric drives again which was a real passion of mine.”</p>
<p>Over his 30-year career in the Navy, Goddard worked on updating their fleet with the latest cutting-edge technology. He was involved in the then top-secret project Sea Shadow, which sought to build a stealth ship, and worked as a program manager for the construction of the large destroyer DDG-1000. After his promotion to admiral, he was tasked with overseeing a dozen ship design and building programs as program executive officer for ships for the Navy. He retired from the Navy in 2008 to enter the private sector.</p>
<p>Goddard first joined Fincantieri in 2011, when he was asked to manage their shipyard along the Menominee River in Marinette, Wisconsin. “Actually, building ships in a shipyard was always one of my bucket list items,” he adds.</p>
<p>In his current role, Goddard is overseeing Fincantieri’s participation in the Next Generation Frigate FFG(X) Program. If the design of the ITS Alpino is chosen next year by the U.S. Navy, he and his team will work on incorporating U.S. radars, sonars, and combat systems within the existing design. This processing of taking an existing ship and converting it for a different role or mission is something MIT students get exposure to.</p>
<p>“It’s similar to a project you have to complete in MIT’s naval architecture program,” Goddard explains. “When the students were on board the Alpino, I was chatting a lot with them about their projects and what the challenges are with converting ships.”</p>
<p>For Goddard, FFG(X) project is a perfect bookend to his career designing and building naval ships. “I got to a design naval ships inside the Navy, and now I get to design one outside the Navy,” he adds.</p>
<p>While aboard the Alpino in Boston Harbor, Goddard announced that Fincantieri Marine Group has pledged $50,000 over the course of the next five years to support MIT’s Ocean Engineering Research and Development Fund.</p>
The Italian naval warship ITS Alpino (foreground) sails alongside the USS Constitution in Boston Harbor on June 8, 2018. Photo: Fincantieri Marinette MarineAlumni/ae, Mechanical engineering, Navy, Security studies and military, Oceanography and ocean engineeringAlbatross robot takes flighthttps://news.mit.edu/2018/albatross-robot-takes-flight-0518
Autonomous glider can fly like an albatross, cruise like a sailboat.Fri, 18 May 2018 00:00:00 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2018/albatross-robot-takes-flight-0518<p>MIT engineers have designed a robotic glider that can skim along the water’s surface, riding the wind like an albatross while also surfing the waves like a sailboat.</p>
<p>In regions of high wind, the robot is designed to stay aloft, much like its avian counterpart. Where there are calmer winds, the robot can dip a keel into the water to ride like a highly efficient sailboat instead.</p>
<p>The robotic system, which borrows from both nautical and biological designs, can cover a given distance using one-third as much wind as an albatross and traveling 10 times faster than a typical sailboat. The glider is also relatively lightweight, weighing about 6 pounds. The researchers hope that in the near future, such compact, speedy robotic water-skimmers may be deployed in teams to survey large swaths of the ocean.</p>
<p>“The oceans remain vastly undermonitored,” says Gabriel Bousquet, a former postdoc in MIT’s Department of Aeronautics and Astronautics, who led the design of the robot as part of his graduate thesis. “In particular, it’s very important to understand the Southern Ocean and how it is interacting with climate change. But it’s very hard to get there. We can now use the energy from the environment in an efficient way to do this long-distance travel, with a system that remains small-scale.”</p>
<p>Bousquet will present details of the robotic system this week at IEEE’s International Conference on Robotics and Automation, in Brisbane, Australia. His collaborators on the project are Jean-Jacques Slotine, professor of mechanical engineering and information sciences and of brain sciences; and Michael Triantafyllou, the Henry L. and Grace Doherty Professor in Ocean Science and Engineering.</p>
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<p><strong>The physics of speed</strong></p>
<p>Last year, Bousquet, Slotine, and Triantafyllou published a study on <a href="http://news.mit.edu/2017/engineers-identify-key-albatross-marathon-flight-1011">the dynamics of albatross flight</a>, in which they identified the mechanics that enable the tireless traveler to cover vast distances while expending minimal energy. The key to the bird’s marathon voyages is its ability to ride in and out of high- and low-speed layers of air.</p>
<p>Specifically, the researchers found the bird is able to perform a mechanical process called a “transfer of momentum,” in which it takes momentum from higher, faster layers of air, and by diving down transfers that momentum to lower, slower layers, propelling itself without having to continuously flap its wings.</p>
<p>Interestingly, Bousquet observed that the physics of albatross flight is very similar to that of sailboat travel. Both the albatross and the sailboat transfer momentum in order to keep moving. But in the case of the sailboat, that transfer occurs not between layers of air, but between the air and water.</p>
<p>“Sailboats take momentum from the wind with their sail, and inject it into the water by pushing back with their keel,” Bousquet explains. “That’s how energy is extracted for sailboats.”</p>
<p><img alt="" src="/sites/mit.edu.newsoffice/files/albatross-robot.gif" /></p>
<p class="caption"><span style="font-size:10px;">An albatross glider, designed by MIT engineers, skims the Charles River.</span></p>
<p>Bousquet also realized that the speed at which both an albatross and a sailboat can travel depends upon the same general equation, related to the transfer of momentum. Essentially, both the bird and the boat can travel faster if they can either stay aloft easily or interact with two layers, or mediums, of very different speeds.</p>
<p>The albatross does well with the former, as its wings provide natural lift, though it flies between air layers with a relatively small difference in windspeeds. Meanwhile, the sailboat excels at the latter, traveling between two mediums of very different speeds — air versus water — though its hull creates a lot of friction and prevents it from getting much speed.&nbsp; Bousquet wondered: What if a vehicle could be designed to perform well in both metrics, marrying the high-speed qualities of both the albatross and the sailboat?</p>
<p>“We thought, how could we take the best from both worlds?” Bousquet says.</p>
<p><strong>Out on the water</strong></p>
<p>The team drafted a design for such a hybrid vehicle, which ultimately resembled an autonomous glider with a 3-meter wingspan, similar to that of a typical albatross. They added a tall, triangular sail, as well as a slender, wing-like keel. They then performed some mathematical modeling to predict how such a design would travel.</p>
<p>According to their calculations, the wind-powered vehicle would only need relatively calm winds of about 5 knots to zip across waters at a velocity of about 20 knots, or 23 miles per hour.</p>
<p>“We found that in light winds you can travel about three to 10 times faster than a traditional sailboat, and you need about half as much wind as an albatross, to reach 20 knots,” Bousquet says. “It’s very efficient, and you can travel very fast, even if there is not too much wind.”</p>
<p>The team built a prototype of their design, using a glider airframe designed by Mark Drela, professor of aeronautics and astronautics at MIT. To the bottom of the glider they added a keel, along with various instruments, such as GPS, inertial measurement sensors, auto-pilot instrumentation, and ultrasound, to track the height of the glider above the water.</p>
<p>“The goal here was to show we can control very precisely how high we are above the water, and that we can have the robot fly above the water, then down to where the keel can go under the water to generate a force, and the plane can still fly,” Bousquet says.</p>
<p>The researchers decided to test this “critical maneuver” — the act of transitioning between flying in the air and dipping the keel down to sail in the water. Accomplishing this move doesn’t necessarily require a sail, so Bousquet and his colleagues decided not to include one in order to simplify preliminary experiments.</p>
<p>In the fall of 2016, the team put its design to the test, launching the robot from the MIT Sailing Pavilion out onto the Charles River. As the robot lacked a sail and any mechanism to get it started, the team hung it from a fishing rod attached to a whaler boat. With this setup, the boat towed the robot along the river until it reached about 20 miles per hour, at which point the robot autonomously “took off,” riding the wind on its own.</p>
<p>Once it was flying autonomously, Bousquet used a remote control to give the robot a “down” command, prompting it to dip low enough to submerge its keel in the river. Next, he adjusted the direction of the keel, and observed that the robot was able to steer away from the boat as expected. He then gave a command for the robot to fly back up, lifting the keel out of the water.</p>
<p>“We were flying very close to the surface, and there was very little margin for error — everything had to be in place,” Bousquet says. “So it was very high stress, but very exciting.”</p>
<p>The experiments, he says, prove that the team’s conceptual device can travel successfully, powered by the wind and the water. Eventually, he envisions fleets of such vehicles autonomously and efficiently monitoring large expanses of the ocean.</p>
<p>“Imagine you could fly like an albatross when it’s really windy, and then when there’s not enough wind, the keel allows you to sail like a sailboat,” Bousquet says. “This dramatically expands the kinds of regions where you can go.”</p>
<p>This research was supported, in part, by the Link Ocean Instrumentation fellowship.</p>
An albatross glider, designed by MIT engineers, skims the Charles River.Photo: Gabriel BousquetAeronautical and astronautical engineering, Drones, Autonomous vehicles, Mechanical engineering, Oceanography and ocean engineering, Research, Robots, Robotics, School of EngineeringFundamental equations guide marine robots to optimal sampling sites https://news.mit.edu/2018/fundamental-equations-guide-marine-robots-optimal-sampling-sites-0510
New principled approach helps autonomous underwater vehicles explore the ocean in an intelligent, energy-efficient manner. Wed, 09 May 2018 23:59:59 -0400MIT News Officehttps://news.mit.edu/2018/fundamental-equations-guide-marine-robots-optimal-sampling-sites-0510<p>Observing the world’s oceans is increasingly a mission assigned to autonomous underwater vehicles (AUVs) — marine robots that are designed to drift, drive, or glide through the ocean without any real-time input from human operators. Critical questions that AUVs can help to answer are where, when, and what to sample for the most informative data, and how to optimally reach sampling locations.</p>
<p>MIT engineers have now developed systems of mathematical equations that forecast the most informative data to collect for a given observing mission, and the best way to reach the sampling sites.</p>
<p>With their method, the researchers can predict the degree to which one variable, such as the speed of ocean currents at a certain location, reveals information about some other variable, such as temperature at some other location — a quantity called “mutual information.” If the degree of mutual information between two variables is high, an AUV can be programmed to go to certain locations to measure one variable, to gain information about the other. &nbsp;</p>
<p>The team used their equations and an ocean model they developed, called &nbsp;Multidisciplinary Simulation, Estimation, and Assimilation Systems (MSEAS), in sea experiments to successfully forecast fields of mutual information and guide actual AUVs.</p>
<p>“Not all data are equal,” says Arkopal Dutt, a graduate student in MIT’s Department of Mechanical Engineering. “Our criteria … allow the autonomous machines to pinpoint sensor locations and sampling times where the most informative measurements can be made.”</p>
<p>To determine how to safely and efficiently reach ideal sampling destinations, the researchers developed a way to help AUVs use the uncertain ocean’s activity, by forecasting out a “reachability front” — a dynamic three-dimensional region of the ocean that an AUV would be guaranteed to reach within a certain time, given the AUV’s power constraints and the ocean’s currents. The team’s method enables a vehicle to surf currents that would bring it closer to its destination, and avoid those that would throw it off track.</p>
<p>When the researchers compared their reachability forecasts with the routes of actual AUVs observing a region of the Arabian Sea, they found their predictions matched where the vehicles were able to navigate, over long periods of time.</p>
<p>Ultimately, the team’s methods should help vehicles explore the ocean in an intelligent, energy-efficient manner.</p>
<p>“Autonomous marine robots are our scouts, braving the rough seas to collect data for us,” says mechanical engineering graduate student Deepak Subramani. “Our math equations help the scouts reach the desired locations and reduce their energy usage by intelligently using the ocean currents.”</p>
<p>The researchers, led by Pierre Lermusiaux, professor of mechanical engineering and ocean science and engineering at MIT, have laid out their results in a paper soon to appear in a volume of the book series, “The Sea,” published by the <em>Journal of Marine Research.</em></p>
<p>In addition to Dutt and Subramani, Lermusiaux’s team includes Jing Lin, Chinmay Kulkarni, Abhinav Gupta, Tapovan Lolla, Patrick Haley, Wael Hajj Ali, Chris Mirabito, and Sudip Jana, all from the Department of Mechanical Engineering.</p>
<p><strong>Quest for the most informative data </strong></p>
<p>To validate their approach, the researchers showed that they could successfully predict the measurements that were the most informative for a varied set of goals. For example, they forecast the observations that were optimal for testing scientific hypotheses, learning if the ocean model equations themselves are correct or not, estimating parameters of marine ecosystems, and detecting the presence of coherent structures in the ocean. They confirmed that their optimal observations were 50 to 150 percent more informative than an average observation.</p>
<p>To reach the optimal observing locations, AUVs must navigate through the ocean. Traditionally, planning paths for robots has been done in relatively static environments. But planning through the ocean is a different story, as strong currents and eddies can constantly change, be uncertain, and push a vehicle off its preplanned course.</p>
<p>The MIT team thus developed path-planning algorithms from fundamental principles with the ocean in mind. They modified an existing equation, known as the Hamilton-Jacobi equation, to determine an AUV’s reachability front, or the furthest perimeter a vehicle is guaranteed to reach in a given amount of time. The equation is based on three main variables: time, a vehicle’s specific propulsion constraints, and advection, or the transport by the dynamic ocean currents — a variable which the group predicts by using its MSEAS ocean model.</p>
<p>With the new system, the AUVs can map out the feasible most informative paths and adapt their sampling plans as the uncertain ocean’s currents shift over time. In a first large, open-ocean test, the team calculated probabilistic reachability fronts and the most informative paths for autonomous floats and gliders in the Indian Ocean, as part of the <a href="http://mseas.mit.edu/Research/NASCar-OPS/index.html">Northern Arabian Sea Circulation-autonomous research (NASCar) initiative</a> of the Office of Naval Research (ONR).</p>
<p>Over several months, the researchers, working out of their MIT offices, provided daily reachability forecasts to the ONR team to help guide the underwater vehicles, collecting optimal observations along the way.</p>
<p>“It was basically not much sleeping,” Lermusiaux recalls. “The forecasts were three to seven days out, and we would assimilate data and update every day. We did quite well. On average, the gliders and floats ended up where desired and within the probabilistic areas that we predicted.”</p>
<p><strong>A moment of truth pays off</strong></p>
<p>Lermusiaux and his colleagues also utilized their systems to plan “time-optimal paths” — trajectories that would get an AUV to a certain location in the shortest amount of time, given the forecast ocean current conditions.</p>
<p>With colleagues from the MIT Lincoln Laboratory and Woods Hole Oceanographic Institution, they tested these time-optimal paths in real time by holding “races” between identical propelled AUVs, off the coast of Martha’s Vineyard. In each race, one AUV’s course was determined by the team’s time-optimal path, while another AUV followed a path with the shortest distance to the same destination.</p>
<p>“It was tense — who will win?” Subramani recalls. “This was the moment of truth for us, after all those years of theoretical development with math equations and proofs.”</p>
<p>The team’s work paid off. In every race, the AUV operating under the team’s forecast reached its destination first, performing about 15 percent faster than the competing AUV. The team’s forecast helped the winning AUV to avoid strong currents that at times acted to block the other AUV.</p>
<p>“It was amazing,” Kulkarni says. “Even though physically the two paths were only less than a mile apart, following our predictions gave up to a 15 percent reduction in travel times. It shows our paths are truly time optimal.”</p>
<p>Among other applications, Lermusiaux, as a member of MIT’s Tata Center for Technology and Design, will be applying his ocean forecasting methods to help guide observations off the coast of India, where the vehicles will be tasked with monitoring fisheries to provide a potentially low-cost management system.</p>
<p>“AUVs are not very fast, and their autonomy is not infinite, so you really have to take into account the currents and their uncertainties, and model things rigorously,” Lermusiaux says. “Machine intelligence for these autonomous systems comes from rigorously deriving and merging governing differential equations and principles with control theory, information theory, and machine learning.”</p>
<p>This research was funded, in part, by the Office of Naval Research, the MIT Lincoln Laboratory, the MIT Tata Center, and the National Science Foundation.</p>
WHOI and MIT researchers deploy an autonomous underwater vehicle to test new navigation and sensing algorithms.Image: MSEASAutonomous vehicles, Computer modeling, Fluid dynamics, Machine learning, Mechanical engineering, Oceanography and ocean engineering, Research, School of Engineering, Tata Center, Lincoln Laboratory, National Science Foundation (NSF)Understanding microbial competition for nitrogenhttps://news.mit.edu/2018/understanding-microbial-competition-for-nitrogen-0410
Interactions among microorganisms account for nitrite accumulation just below the sunlit zone, with implications for oceanic carbon and nitrogen cycling.Tue, 10 Apr 2018 14:30:01 -0400Lauren Hinkel | Oceans at MIThttps://news.mit.edu/2018/understanding-microbial-competition-for-nitrogen-0410<p>Nitrogen is a hot commodity in the surface ocean. Primary producers including phytoplankton and other microorganisms consume and transform it into organic molecules to build biomass, while others transform inorganic forms to access their chemical store of energy. All of these steps are part of the complex nitrogen cycle of the upper water column.</p>
<p>About 200 meters down, just below the ocean’s sunlit zone, resides a layer of nitrite, an intermediate compound in the nitrogen cycle. Scientists have found this robust feature, called the primary nitrite maximum, throughout the world’s oxygenated oceans. While several individual hypotheses have been put forward, none have convincingly explained this marine signature until now.</p>
<p>A recent <em>Nature Communications</em>&nbsp;<a href="http://www.nature.com/articles/s41467-018-03553-w" target="_blank">study</a> led by researchers in the Program in Atmospheres, Oceans and Climate (<a href="http://paocweb.mit.edu/" target="_blank">PAOC</a>) within MIT’s Department of Earth, Atmospheric and Planetary Sciences (<a href="http://eapsweb.mit.edu/" target="_blank">EAPS</a>) uses theory, modeling, and observational data to investigate the ecological mechanisms producing the observed nitrite accumulation and dictating its location in the water column. Lead author <a href="http://ezakem.scripts.mit.edu/emilyzakem/" target="_blank">Emily Zakem</a> — a former EAPS graduate student who is now a postdoc at the University of Southern California — along with EAPS Principal Research Scientist&nbsp;<a href="http://paocweb.mit.edu/people/stephdut" target="_blank">Stephanie Dutkiewicz</a>&nbsp;and Professor&nbsp;<a href="http://paocweb.mit.edu/people/mick" target="_blank">Mick Follows&nbsp;</a>show that physiological constraints and resource competition between phytoplankton and nitrifying microorganisms in the sunlit layer can yield this ocean trait.&nbsp;</p>
<p><strong>Regulating the biological pump</strong></p>
<p>Despite its low oceanic concentration, nitrite (NO<sub>2</sub><sup>-</sup>) plays a key role in global carbon and nitrogen cycles. Most of the nitrogen in the ocean resides in the inorganic form of nitrate (NO<sub>3</sub><sup>-</sup>), which primary producers and microorganisms chemically reduce it to build organic molecules. Remineralization occurs when the reverse process takes place: Phytoplankton and other heterotrophic bacteria break down these organic compounds into ammonium (NH<sub>4</sub><sup>+</sup>), a form of inorganic nitrogen. Ammonium then can be consumed again by primary producers, which get their energy from light. Other microorganisms called chemoautotrophs also use the ammonium both to make new biomass and as a source of energy. To do this, they extract oxygen from seawater and transform it, a process called nitrification, which occurs in two steps. First, the microbes convert ammonium into nitrite and then to nitrate.</p>
<p>Somewhere along the line, nitrite has been accumulating at the base of the sunlit zone, which has implications for ocean biogeochemistry. “Broadly, we’re trying to understand what controls the remineralization of organic matter in the ocean. It’s that remineralization that is responsible for forming the biological pump, which is the extra storage of carbon in the ocean due to biological activity,” says Zakem. It’s this strong influence that nitrogen has on the global carbon cycle that captures Follows’ interest. “Growth of phytoplankton on nitrate is called ‘new production’ and that balances the amount that’s sinking out of the surface and controls how much carbon is stored in the ocean. Growth of phytoplankton on ammonium is called recycled production, which does not increase ocean carbon storage,” Follows says. “So we wish to understand what controls the rates of supply and relative consumption of these different nitrogen species.”</p>
<p><strong>Battle for nitrogen</strong>&nbsp;</p>
<p>The primary nitrite maximum resides between two groups of microorganisms in most of the world’s oceans. Above it in the sunlit zone are the phytoplankton, and in the primary nitrite maximum and slightly below that rest an abundance of nitrifying microbes in an area with high rates of nitrification. Researchers classify these microbes into two groups based on their preferred nitrogen source: the ammonium oxidizing organisms (AOO) and nitrite oxidizing organisms (NOO). In high latitudes like the Earth’s subpolar regions, nitrite accumulates in the surface sunlit zone as well as deeper.</p>
<p>Scientists have postulated that there might be two not mutually exclusive reasons for the build-up of nitrite: Nitrification by chemoautotrophic microbes, and when stressed, phytoplankton can reduce nitrate to nitrite. Since isotopic evidence does not support the latter, the group looked into the former.&nbsp;</p>
<p>“The long-standing hypothesis was that the locations of nitrification were controlled by the inhibition of light of these [nitrifying] microorganisms, so the microorganisms that carry out this process were restricted from the surface,” Zakem says, implying that these nitrifying chemoautotrophs got sunburned. But instead of assuming that was true, the group examined the ecological interactions among these and other organisms in the surface ocean, letting the dynamics fall out naturally. To do this they collected microbial samples from the subtropical North Pacific and evaluated them for metabolism rates, efficiencies and abundances, and assessed the physiological needs and constraints of the different nitrifying microbes by reducing the biological complexity of their metabolisms down to its underlying chemistry and thus hypothesizing some of the more fundamental constrains. They used this information to inform the dynamics of the nitrifying microbes in both a one-dimensional and three-dimensional biogeochemical model.</p>
<p>The group found that by employing this framework, they could resolve the interactions between these nitrifying chemoautotrophs and phytoplankton and therefore simulate the accumulation of nitrite at the primary nitrite maximum in the appropriate locations. In the surface ocean when inorganic nitrogen is a limiting factor, phytoplankton and ammonium oxidizing microbes have similar abilities to acquire ammonium, but because phytoplankton need less nitrogen to grow and have a faster growth rate, they are able to outcompete the nitrifiers, excluding them from the sunlit zone. In this way, they were able to provide an ecological explanation for where nitrification happens without having to rely on light inhibition dictating the location.</p>
<p>Comparing the fundamental physiologies of the nitrifiers revealed that differences in metabolisms and cell size could account for the nitrite build-up. The researchers found that the second step of the nitrification process that’s carried out by the nitrite oxidizers requires more nitrogen for the same amount of biomass being created by these organisms, meaning that the ammonia oxidizers can do more with less, and that there are fewer nitrite oxidizers than the ammonia oxidizers. The nitrite oxidizing microbes also have a higher surface to volume constraint than the smaller and ubiquitous ammonium oxidizing microbes, making nitrogen uptake more difficult. “This is an alternative explanation for why nitrite should accumulate,” Zakem says. “We have two reasons that point in the same direction. We can’t distinguish which one it is, but all of the observations are consistent with either of these two or some combination of both being the control.”</p>
<p>The researchers were also able use a global climate model to reproduce an accumulation of nitrite in the sunlit zone of places like subpolar regions, where phytoplankton are limited by another resource other than nitrogen like light or iron. Here, nitrifiers can co-exist with phytoplankton since there’s more nitrogen available to them. Additionally, the deep mixed layer in the water can draw resources away from the phytoplankton, giving the nitrifiers a better chance at survival in the surface.</p>
<p>“There’s this long standing hypothesis that the nitrifiers were inhibited by light and that’s why they only exist at the subsurface,” Zakem says. “We’re saying that maybe we have a more fundamental explanation: that this light inhibition does exist because we’ve observed it, but that’s a consequence of long-term exclusion from the surface.”</p>
<p><strong>Thinking bigger</strong></p>
<p>“This study pulled together theory, numerical simulations, and observations to tease apart and provide a simple quantitative and mechanistic description for some phenomena that were mysterious in the ocean,” Follows says. “That helps us tease apart the nitrogen cycle, which has an impact on the carbon cycle. It's also opened up the box for using these kind of tools to address other questions in the microbial oceanography.” He notes that the fact that these microbes are shunting ammonium into nitrate near the sunlit zone complicates the story of carbon storage in the ocean.</p>
<p>Two researchers who were not involved with the study, Karen Casciotti, associate professor in the Stanford University Department of Earth System Science, and Angela Landolfi, a scientist in the&nbsp;marine biogeochemical modeling department at the GEOMAR Helmholtz Centre for Ocean&nbsp;Research Kiel, agree. “This study is of great significance as it provides evidence of how organisms’ individual traits affect competitive interactions among microbial populations and provide a direct control on nutrients' distribution in the ocean,” says Landolfi. “In essence Zakem et al., provide a better understanding of the link between different levels of complexity from individual- to community up to environmental level, providing a mechanistic framework to predict changes in community composition and their biogeochemical impact under climatic changes,” says Landolfi.</p>
<p>This research was funded by the Simons Foundation’s Simons Collaboration on Ocean Processes and Ecology, the Gordon and Betty Moore Foundation, and the National Science Foundation.</p>
New MIT research describes how marine microorganisms contribute to a layer of nitrite just below the ocean's sunlit zone.Research, Microbiology, Chemistry, Biology, Oceanography and ocean engineering, Ocean science, Microbes, Carbon, Ecology, EAPS, School of ScienceSoft robotic fish swims alongside real ones in coral reefshttps://news.mit.edu/2018/soft-robotic-fish-swims-alongside-real-ones-coral-reefs-0321
Made of silicone rubber, CSAIL’s “SoFi” could enable a closer study of aquatic life.
Wed, 21 Mar 2018 13:59:59 -0400Adam Conner-Simons | CSAILhttps://news.mit.edu/2018/soft-robotic-fish-swims-alongside-real-ones-coral-reefs-0321<p>This month scientists published <a href="https://www.smithsonianmag.com/science-nature/caught-camera-ancient-greenland-sharks-180968303/" style="text-decoration:none;">rare footage</a> of one of the Arctic’s most elusive sharks. The findings demonstrate that, even with many technological advances in recent years, it remains a challenging task to document marine life up close.</p>
<p>But MIT computer scientists believe they have a possible solution: using robots.</p>
<p>In a paper out today, a team from MIT’s <a href="https://www.csail.mit.edu/">Computer Science and Artificial Intelligence Laboratory</a> (CSAIL) unveiled “SoFi,” a soft robotic fish that can independently swim alongside real fish in the ocean.</p>
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<p>During test dives in the Rainbow Reef in Fiji, SoFi swam at depths of more than 50 feet for up to 40 minutes at once, nimbly handling currents and taking high-resolution photos and videos using (what else?) a fisheye lens.</p>
<p>Using its undulating tail and a unique ability to control its own buoyancy, SoFi can swim in a straight line, turn, or dive up or down. The team also used a waterproofed Super Nintendo controller and developed a custom acoustic communications system that enabled them to change SoFi’s speed and have it make specific moves and turns.</p>
<p>“To our knowledge, this is the first robotic fish that can swim untethered in three dimensions for extended periods of time,” says CSAIL PhD candidate Robert Katzschmann, lead author of the new journal article published today in <em>Science</em> <em>Robotics</em>. “We are excited about the possibility of being able to use a system like this to get closer to marine life than humans can get on their own.”</p>
<p>Katzschmann worked on the project and wrote the paper with CSAIL director Daniela Rus, graduate student Joseph DelPreto and former postdoc Robert MacCurdy, who is now an assistant professor at the University of Colorado at Boulder.</p>
<p><strong>How it works</strong></p>
<p>Existing autonomous underwater vehicles (AUVs) have traditionally been tethered to boats or powered by bulky and expensive propellers.</p>
<p>In contrast, SoFi has a much simpler and more lightweight setup, with a single camera, a motor, and the same lithium polymer battery that’s found in consumer smartphones. To make the robot swim, the motor pumps water into two balloon-like chambers in the fish’s tail that operate like a set of pistons in an engine. As one chamber expands, it bends and flexes to one side; when the actuators push water to the other channel, that one bends and flexes in the other direction.</p>
<p>These alternating actions create a side-to-side motion that mimics the movement of a real fish. By changing its flow patterns, the hydraulic system enables different tail maneuvers that result in a range of swimming speeds, with an average speed of about half a body length per second.</p>
<p>“The authors show a number of technical achievements in fabrication, powering, and water resistance that allow the robot to move underwater without a tether,” says Cecilia Laschi, a professor of biorobotics at the Sant'Anna School of Advanced Studies in Pisa, Italy. “A robot like this can help explore the reef more closely than current robots, both because it can get closer more safely for the reef and because it can be better accepted by the marine species.”</p>
<p>The entire back half of the fish is made of silicone rubber and flexible plastic, and several components are 3-D-printed, including the head, which holds all of the electronics. To reduce the chance of water leaking into the machinery, the team filled the head with a small amount of baby oil, since it’s a fluid that will not compress from pressure changes during dives.</p>
<p>Indeed, one of the team’s biggest challenges was to get SoFi to swim at different depths. The robot has two fins on its side that adjust the pitch of the fish for up and down diving. To adjust its position vertically, the robot has an adjustable weight compartment and a “buoyancy control unit” that can change its density by compressing and decompressing air.</p>
<p>Katzschmann says that the team developed SoFi with the goal of being as nondisruptive as possible in its environment, from the minimal noise of the motor to the ultrasonic emissions of the team’s communications system, which sends commands using wavelengths of 30 to 36 kilohertz.</p>
<p>“The robot is capable of close observations and interactions with marine life and appears to not be disturbing to real fish,” says Rus.</p>
<p>The project is part of a larger body of work at CSAIL focused on soft robots, which have the potential to be safer, sturdier, and more nimble than their hard-bodied counterparts. Soft robots are in many ways easier to control than rigid robots, since researchers don’t have to worry quite as much about having to avoid collisions.</p>
<p>“Collision avoidance often leads to inefficient motion, since the robot has to settle for a collision-free trajectory,” says Rus, the Andrew and Erna Viterbi Professor of Electrical Engineering and Computer Science at MIT. “In contrast, a soft robot is not just more likely to survive a collision, but could use it as information to inform a more efficient motion plan next time around.”</p>
<p>As next steps the team will be working on several improvements on SoFi. Katzschmann plans to increase the fish’s speed by improving the pump system and tweaking the design of its body and tail.</p>
<p>He says that they also plan to soon use the on-board camera to enable SoFi to automatically follow real fish, and to build additional SoFis for biologists to study how fish respond to different changes in their environment.</p>
<p>“We view SoFi as a first step toward developing almost an underwater observatory of sorts,” says Rus. “It has the potential to be a new type of tool for ocean exploration and to open up new avenues for uncovering the mysteries of marine life.”</p>
<p>This project was supported by the National Science Foundation.</p>
Using its undulating tail and a unique ability to control its own buoyancy, SoFi can swim in a straight line, turn, or dive up or down. Photo: Joseph DelPreto/MIT CSAILResearch, Robotics, Computer Science and Artificial Intelligence Laboratory (CSAIL), Robots, Electrical Engineering & Computer Science (eecs), Soft robotics, Actuators, Distributed Robotics Laboratory, School of Engineering, Artificial intelligence, 3-D printing, Additive manufacturing, Biomimetics, Oceanography and ocean engineering, National Science Foundation (NSF)Stefan Helmreich conducts fieldwork aboard the unique FLIP shiphttps://news.mit.edu/2018/stefan-helmreich-conducts-fieldwork-aboard-unique-flip-ship-0216
MIT anthropologist is researching how scientists understand waves.Fri, 16 Feb 2018 17:40:01 -0500School of Humanities, Arts, and Social Scienceshttps://news.mit.edu/2018/stefan-helmreich-conducts-fieldwork-aboard-unique-flip-ship-0216<p>The author of the award-winning book “Alien Ocean: Anthropological Voyages in Microbial Seas,” MIT anthropologist Stefan Helmreich has a wealth of experience examining how scientists think about the world. And recently, he gained a new perspective — quite literally — by taking his research to the Floating Instrument Platform, known colloquially as the FLIP ship.<br />
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Operated by the Scripps Institution of Oceanography in La Jolla, California, the FLIP ship is a unique scientific vessel that can operate in either a horizontal or vertical position. “Everyday life on the ship has an M. C. Escher sort of feel, with doors, sinks, and stairs appearing in both vertical and horizontal alignments,” says Helmreich, who is the Elting E. Morison Professor of Anthropology and head of anthropology within the School of Humanities, Arts, and Social Sciences.<br />
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Helmreich boarded FLIP in October of 2017 to conduct anthropological fieldwork into contemporary ocean wave science — seeking to understand more about the changing theories, models, and technologies that physical oceanographers use to apprehend waves. While aboard ship, he conducted interviews and joined people in their everyday work to learn how they engage with and understand the surface of the sea.</p>
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<p>&nbsp;<strong>Waves are both a physical and cultural reality</strong><br />
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“Wave science is a field with relevance to everything from weather and hurricane prediction, to surf forecasts, to coastal and ocean engineering, to operations research, to shipping, to climate change science, and more,” says Helmreich — whose book "Alien Ocean" drew praise from the journal <em>Nature</em> for capturing “the excitement and crucial nature of oceanographic research.”<br />
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In his current research, Helmreich emphasizes that waves are not only physical phenomena; they are entities that become scientifically legible through measurement, models, and theories — that is, through human cultural activity.<br />
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Within this framing, a range of questions become available, from “How have scientists come to think of ocean waves as populations and statistical processes?” to “How do mathematical conceptualizations of waves relate to the everyday vocabularies of seafarers, shipbuilders, and surfers?”</p>
<p><strong>Aboard the FLIP ship</strong><br />
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On FLIP, Helmreich had the opportunity to investigate such questions while getting to know a unique vessel. In its horizontal conformation, the FLIP travels like an ordinary oceangoing vessel. But by “flipping” 90 degrees into a vertical position once it arrives at its destination, it can become, essentially, a enormous spar buoy.<br />
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“In this position, the vessel looks like nothing so much as a floating metal treehouse,” says Helmreich. With most of the platform’s 108-meter length below the surface, scientists have the rare opportunity to work on the open ocean in a remarkably stable environment. FLIP has been a significant instrument in the long history of U.S.-based wave science, permitting scientists to investigate underwater acoustics, to capture the varied spectrum of ocean waves, and much else.<br />
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What did Helmreich learn on FLIP? Helmreich says that he became particularly fascinated by the work of oceanographers who were using novel laser technologies — operating in visible and invisible frequencies — to make precise measurements of ocean turbulence at the sea surface, where wind and waves interact in ways that are still not fully characterized.<br />
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<strong>The media of comprehension</strong><br />
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What struck him — aside from the experience of doing fieldwork on a ship on which everything seemed sideways — was how wave scientists apprehend their data through cameras and computer screens that present frame-by-frame, color-coded visualizations of the wave field.<br />
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“This mode of understanding waves reminded me of the technology of cinema — even recalling to me an 1891 film called ‘La Vague,’ made by Étienne Jules Marey to study the movement of a wave in the Bay of Naples,” says Helmreich.</p>
<p>“In important ways, wave science is enabled by the media — photographic,&nbsp;computational, acoustic —&nbsp;that scientists employ to comprehend ocean wave generation, propagation, breaking, and more,” he adds.<br />
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<strong>Gravitational, cardiac, symbolic, and gendered</strong><br />
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Back on land, Helmreich continues to extend his research on waves to a wide range of disparate phenomena that employ the same abstract concept. Drawing on media theory and sound studies, for example, he has lately asked, in an essay in <a href="https://www.thewire.co.uk/in-writing/essays/cosmic-chirp" target="_blank"><em>Wire</em></a> magazine, how we should understand the sounds of gravitational wave detection (a related article in <a href="https://doi.org/10.14506/ca31.4.02" target="_blank"><em>Cultural Anthropology</em></a> drew on interviews with MIT physicists Nergis Mavalvala, Scott Hughes, and David Kaiser), and in an article in <a href="https://dx.doi.org/10.1086/670968" target="_blank"><em>Current Anthropology</em></a>, how medical measures of cardiac waves have changed health care.</p>
<p>In a recent essay in <a href="http://dx.doi.org/10.1353/wsq.2017.0015" target="_blank"><em>Women</em>’<em>s Studies Quarterly</em></a>, a feminist studies journal, Helmreich also explores how ocean waves have been described with gendered symbolism in mythology, literature, and social theory. Here is an excerpt from his thought-provoking article, “Potential Energy and the Body Electric,” in <em>Current Anthropology</em>:<br />
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“An orienting note: waves are tricky to think about. Waves are not merely material processes of energy propagation or of vibration. They are also abstractions crafted by scientists who decide what will count as wave activity, whether in a passive medium (as with water waves, sound waves), an excitable medium (as with cardiac and brain waves), or in a vacuum (as with light waves or radio waves; Barad 2007). Literary critic Gillian Beer (1996) has examined the popular reception of wave theory in physics alongside early twentieth-century modernism, noting that both emphasized the transitory and illusory character of the apparently solid world (Beer points readers to the etheric ocean of wireless radio and to Virginia Woolf’s novel of fluid subjectivities ‘The Waves’). Beer suggests that the electromagnetic ‘wave enters the modernist world as a token of a self-conscious relativism about representational schemes. This doubleness is still with us today. Waves are at once processes as well as traces of those processes — traces inscribed in graphs or charts and, less obviously, in the very model of waves that is bound up with their observation.”</p>
<p><em>Story by MIT SHASS Communications<br />
Editorial and Design Director: Emily Hiestand<br />
Senior Writer: Kathryn O'Neil</em></p>
MIT anthropologist Stefan Helmreich on the boom of the FLIP ship in October 2017.Photo courtesy of Stefan HelmreichSHASS, Anthropology, Faculty, Research, Oceanography and ocean engineering, Ocean scienceChaos and climate: Celebrating two pioneers of modern meteorologyhttps://news.mit.edu/2018/mit-chaos-and-climate-celebration-two-pioneers-modern-meteorology-0214
Trailblazing scientists Jule Charney and Edward Lorenz gave us numerical weather prediction and chaos theory, highlighting the value of basic research.Wed, 14 Feb 2018 13:30:00 -0500Lauren Hinkel | Oceans at MIThttps://news.mit.edu/2018/mit-chaos-and-climate-celebration-two-pioneers-modern-meteorology-0214<p>Our understanding of atmospheric and climate dynamics, as well as weather prediction and its limits, would not be what it is today without advances in the fundamental science of modern meteorology that took place at MIT in the post WWII era. Much of this is thanks to two prominent MIT meteorologists born a hundred years ago, but whose work is very much relevant today.</p>
<p>Earlier this month, the Department of Earth, Atmospheric and Planetary Sciences (<a href="http://eapsweb.mit.edu/">EAPS</a>) celebrated the lives and scientific legacies of these two former MIT professors, Edward Norton Lorenz and Jule Gregory Charney, during a two-day symposium:&nbsp;<a href="http://paocweb.mit.edu/about/paoc-spotlights/mit-on-chaos-and-climate">MIT on Chaos and Climate</a>. The event was organized by EAPS faculty from the&nbsp;<a href="http://lorenz.mit.edu/">Lorenz Center</a>&nbsp;and the Program in Atmospheres, Oceans and Climate (PAOC), marking the centennial of the scientists’ birth.</p>
<p>The department brought together the MIT community and friends and welcomed back alumni, and former faculty and scientists from EAPS and the former Department of Meteorology (Course XIX). Also invited were respected colleagues from many scientific fields affected by the work of Charney and Lorenz, including oceanography, meteorology, physics, applied mathematics, and climate science. Together, the group composed of biological and professional families shared vignettes and personal testimonials of the scientists on the first day, and discussed the broader impacts that Charney and Lorenz’s research had on the department and the broader community on the second.</p>
<p><strong>Meteorology’s origins at MIT</strong></p>
<p>Charney and Lorenz were members and chairs of the former Department of Meteorology, which emerged from the country’s first meteorology program founded at MIT by Carl-Gustaf Rossby, considered one of the founders of modern meteorology. In 1983, the department merged with Course XII to become the current EAPS, and was the forefather of PAOC.</p>
<p>The pioneering work of Charney and Lorenz heralded the field of modern meteorology. “It’s fair to say that Jule Charney turned the mystery of the erratic behavior of the atmosphere into a recognizable, although a very, very difficult problem in fluid physics,” said Joe Pedlosky, Woods Hole Oceanographic Institution Emeritus Senior Scientist, on the symposium’s second day.</p>
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<p>Charney’s quasi-geostrophic vorticity equations allowed for concise mathematical description of large-scale atmospheric and oceanic circulations, enabling the numerical weather prediction. Among this and his many fundamental contributions to the field, Charney identified “baroclinic instability,” the mechanism that explains the size, structure, and growth rate of mid-latitude weather systems, and is a ubiquitous phenomenon in rotating, stratified fluids like our oceans and atmosphere. His innovative research provided insights to the theories of weather systems, hydro-dynamical instability, atmospheric wave propagation, hurricanes, drought, desertification, atmospheric blocking, and ocean currents. Many felt the pull of his charisma and academic integrity, falling into “orbit around the Charney sun.” This, along with his idealism and quest for fascinating research results, was the driving force behind many national and international weather initiatives and programs.</p>
<p>“Being in the room with Charney was like being in the room with a tiger, a very friendly tiger,” said David Randall, University Distinguished Professor at Colorado State University.</p>
<p>Lorenz could be considered Charney’s department foil. Many described him as a quiet, humble soul, and in Charney’s words as remembered by Pedlosky, “Lorenz is a genius with a soul of an artist.”</p>
<p>He revolutionized our understanding of atmospheric dynamics and circulation through research into the energetics of stratified, rotating fluids. In “one of the greatest intellectual advances of our time,” Lorenz set out to show that statistical long-range weather forecasting did not perform as well as numerical forecasting, and in the process observed “deterministic chaos,” facts that were&nbsp;highlighted by talks from Kerry Emanuel, the MIT Cecil and Ida Green Professor of Atmospheric Science and co-director of the Lorenz Center, and Tim Palmer, the Royal Society Research Professor at the University of Oxford.</p>
<p>Lorenz’s meticulous research found that infinitesimal differences in initial conditions produced dramatically different forecasts. Chaos theory, popularized as the butterfly effect,&nbsp;shifted our thinking away from deterministic numerical weather prediction to more probabilistic forecasts. “History may well record that Ed Lorenz had hammered the last nail into the coffin of the Cartesian universe,” Emanuel said. Despite the fact that the results of Charney and Lorenz’s research were largely opposing, Palmer noted that their work is now seamlessly intertwined for the benefit of science and society.</p>
<p><strong>Ripples in weather, climate, and beyond earth science</strong></p>
<p>The symposium, through formal and informal presentations, painted a picture of what meteorology was like under the leadership of Lorenz and Charney, and their influence on other fields of study.</p>
<p>On the symposium’s first day, alumni, colleagues, friends, and family shared personal stories of encounters with Charney and Lorenz, including anecdotes about lesser known research and affiliations like Charney’s work with the Union of Concerned Scientists, the discovery of chaos and the jetstream, the study of storm surge in Venice, and MIT’s connection with meteorology in Italy. Mankin Mak, alum of Lorenz’s group and Professor Emeritus at the Department of Atmospheric Sciences at the University of Illinois, even named the “Charney number” after the scientist. All the while, the camaraderie between the Course XIX alumni and excitement to be back in EAPS was palpable, spilling over into the evening’s dinner and the following day.</p>
<p>The second part of the symposium opened to the public and focused on the influence of Lorenz and Charney’s research. This included talks on cloud aggregation, hydrology and atmospheric coupling leading to desertification, oceanography and a realistic model of the Gulf Stream, observation of the turbulent cascade in nonlinear systems, CO2-related climate change, chaos in our solar system, fluid dynamics of pathogen transmission, tipping points in population dynamics, and more.</p>
<p>First-day attendees experienced the extent of the researchers’ work through multimedia. While a slideshow of Lorenz and Charney played, EAPS graduate students&nbsp;Brian Green,&nbsp;Mukund Gupta,&nbsp;Megan Lickley&nbsp;and&nbsp;Santiago Benavides, as well as postdocs&nbsp;Ed Doddridge,&nbsp;Jon Lauderdale,&nbsp;Chris Follett, and&nbsp;Daniel Koll&nbsp;shared posters of their own research during the morning of the symposium’s first day. Two displays were unveiled, which would be hung outside the EAPS Charney Library, across from Charney’s old office on the 14th floor where this groundbreaking work took place, and on the 18th floor. Lab assistant&nbsp;Bill McKenna&nbsp;set up a replica of the LGP-30 computer and printer that Lorenz used for his renowned calculations and showed how it would have been used. Short films from&nbsp;Meg Rosenberg, a producer and editor at MIT Video Productions, and&nbsp;Josh Kastorf, from the Earth Resources Laboratory in EAPS, established timelines of Lorenz and Charney’s life and work at MIT, and explained the origins and implications of chaos theory, respectively.</p>
<p>Charney had once remarked that a “scientist’s interest in the history of his own field was the first sign of senility,” but Raffaele Ferrari, the EAPS Cecil and Ida Green Professor of Oceanography and chair of PAOC, believes that revisiting the past can provide valuable lessons for future thinking and research. “For the students, it must have been inspirational and helpful to see where this department comes from,” Ferrari says. “You realize [that] the history of this department is quite impressive … and the people were here that created this field. … There is no other department like that, definitely [not] in meteorology, that has ever achieved that kind of leadership intellectually on every level.”</p>
<p>By revisiting the group’s history, students could see the evolution of scientific ideas and the values that made the department what it was and that became part of its legacy. In a sentiment echoed by keynote speaker Ernest Moniz, the MIT Cecil and Ida Green Professor Emeritus of Physics and Engineering Systems and special advisor to the MIT President, basic research is the lifeblood of a successful society in the long-term. “[Lorenz and Charney were] thinking about the fundamentals of the problem with students here at MIT,” he said. This practice of fostering curiosity-driven research now underpins the mission of the Lorenz Center: to understand and predict global climate change. “And [that’s] always that you want —&nbsp;to fundamentally understand the problem and then as a result you can make an impact on the real world, on practical applications.”</p>
<p>EAPS professors&nbsp;Ferrari, Emanuel,&nbsp;John Marshall&nbsp;(event MC), Paola Rizzoli,&nbsp;and&nbsp;Dan Rothman&nbsp;organized the symposium. The&nbsp;event was sponsored by the Henry Houghton Fund and the Lorenz Center within EAPS.</p>
<p>Those interested in making&nbsp;a contribution to the Lorenz Center Fund, or to support the renovation of the Charney Library, can contact&nbsp;<a href="http://xeapsweb.mit.edu/people/ellis-angela">Angela Ellis</a>&nbsp;at 617-253-5796 or via email:&nbsp;<a href="mailto:aellis@mit.edu">aellis@mit.edu</a>.</p>
Robert van der Hilst moderates the symposium's day-two panel consisting of Sir Brian Hoskins, Inez Fung, Kerry Emanuel, Allison Wing and John Bush.Photo: Lauren HinkelClimate, Climate change, Oceanography and ocean engineering, School of Science, Earth and atmospheric sciences, EAPS, Lorenz Center, Special events and guest speakers, PhysicsUnlocking marine mysteries with artificial intelligencehttps://news.mit.edu/2017/unlocking-marine-mysteries-artificial-intelligence-1215
Students put their AI software for underwater vehicles to the test on the Charles River. Thu, 14 Dec 2017 23:59:59 -0500Mary Beth O'Leary | Department of Mechanical Engineeringhttps://news.mit.edu/2017/unlocking-marine-mysteries-artificial-intelligence-1215<p>Each year the melting of the Charles River serves as a harbinger for warmer weather. Shortly thereafter is the return of budding trees, longer days, and flip-flops. For students of class 2.680 (Unmanned Marine Vehicle Autonomy, Sensing and Communications), the newly thawed river means it’s time to put months of hard work into practice.</p>
<p>Aquatic environments like the Charles present challenges for robots because of the severely limited communication capabilities. “In underwater marine robotics, there is a unique need for artificial intelligence — it’s crucial,” says MIT Professor Henrik Schmidt, the course’s co-instructor. “And that is what we focus on in this class.”</p>
<p>The class, which is offered during spring semester, is structured around the presence of ice on the Charles. While the river is covered by a thick sheet of ice in February and into March, students are taught to code and program a remotely-piloted marine vehicle for a given mission. Students program with MOOS-IvP, an autonomy software used widely for industry and naval applications.</p>
<p>“They’re not working with a toy,” says Schmidt’s co-instructor, Research Scientist Michael Benjamin. “We feel it’s important that they learn how to extend the software — write their own sensor processing models and AI behavior. And then we set them loose on the Charles.”</p>
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<p>As the students learn basic programming and software skills, they also develop a deeper understanding of ocean engineering. “The way I look at it, we are trying to clone the oceanographer and put our understanding of how the ocean works into the robot,” Schmidt adds. This means students learn the specifics of ocean environments — studying topics like oceanography or underwater acoustics.&nbsp;</p>
<p>Students develop code for several missions they will conduct on the Charles River by the end of the semester. These missions include finding hazardous objects in the water, receiving simulated temperature and acoustic data along the river, and communicating with other vehicles.</p>
<p>“We learned a lot about the applications of these robots and some of the challenges that are faced in developing for ocean environments,” says Alicia Cabrera-Mino ’17, who took the course last spring.</p>
<p>Augmenting robotic marine vehicles with artificial intelligence is useful in a number of fields. It can help researchers gather data on temperature changes in our ocean, inform strategies to reverse global warming, traverse the 95 percent of our oceans that has yet to be explored, map seabeds, and further our understanding of oceanography.</p>
<p>According to graduate student Gregory Nannig, a former navigator in the U.S. Navy, adding AI capabilities to marine vehicles could also help avoid navigational accidents. “I think that it can really enable better decision making,” Nannig explains. “Just like the advent of radar or going from celestial navigation to GPS, we’ll now have artificial intelligence systems that can monitor things humans can’t.”</p>
<p>Students in 2.680 use their newly acquired coding skills to build such systems. Come spring, armed with the software they’ve spent months working on and a better understanding of ocean environments, they enter the MIT Sailing Pavilion prepared to test their artificial intelligence coding skills on the recently melted Charles River.</p>
<p>As marine vehicles glide along the Charles, executing missions based on the coding students have spent the better part of a semester perfecting, the mood is often one of exhilaration. “I’ve had students have big emotions when they see a bit of AI that they’ve created,” Benjamin recalls. “I’ve seen people call their parents from the dock.”</p>
<p>For this artificial intelligence to be effective in the water, students need to combine software skills with ocean engineering expertise. Schmidt and Benjamin have structured 2.680 to ensure students have a working knowledge of these twin pillars of robotic marine vehicle autonomy.</p>
<p>By combining these two research areas in their own research, Schmidt and Benjamin hope to create underwater robots that can go places humans simply cannot. “There are a lot of applications for better understanding and exploring our ocean if we can do it smartly with robots,” Benjamin adds.</p>
Class 2.680 (Unmanned Marine Vehicle Autonomy, Sensing and Communications), which is offered during spring semester, is structured around the presence of ice on the Charles. While the river is covered by a thick sheet of ice in February and into March, students are taught to code and program a remotely-piloted marine vehicle for a given mission.
Image: Teresa LinSchool of Engineering, Mechanical engineering, Artificial intelligence, Autonomous vehicles, Classes and programs, Computer Science and Artificial Intelligence Laboratory (CSAIL), Computer science and technology, Education, teaching, academics, Oceanography and ocean engineering, RobotsOcean sound waves may reveal location of incoming objectshttps://news.mit.edu/2017/ocean-sound-waves-may-reveal-location-incoming-objects-1026
New acoustic analysis could pinpoint impacts by meteorites or possibly plane debris.Thu, 26 Oct 2017 00:00:01 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2017/ocean-sound-waves-may-reveal-location-incoming-objects-1026<p>The ocean can seem like an acoustically disorienting place, with muffled sounds from near and far blending together in a murky sea of noise.</p>
<p>Now an MIT mathematician has found a way to cut through this aquatic cacaphony, to identify underwater sound waves generated by objects impacting the ocean’s surface, such as debris from meteorites or aircraft. The results are published this week in the online journal <em>Scientific Reports</em>.</p>
<p>Lead author Usama Kadri, a research affiliate in MIT’s Department of Mathematics, is applying the team’s acoustic analysis in hopes of locating Malaysia Airlines flight 370, an international passenger plane that disappeared over the southern Indian Ocean on March 8, 2014.</p>
<p>Since the aircraft’s disappearance, authorities have confirmed and recovered a few of the plane’s parts. However, the bulk of the aircraft has yet to be identified, as has any reasonable explanation for its demise.</p>
<p>Kadri believes that if the plane indeed crashed into the ocean, it would have generated underwater sound waves, called acoustic-gravity waves, with a very specific pattern. Such waves travel across large distances before dissipating and therefore would have been recorded by hydrophones around the world. If such patterns can be discerned amid the ocean’s background noise, Kadri says acoustic-gravity waves can be traced back to the location of the original crash.</p>
<p>In this new paper, Kadri and his colleagues have identified a characteristic pattern of acoustic-gravity waves produced by impacting objects, as opposed to other sources such as earthquakes or underwater explosions. They have looked for this pattern in data collected by underwater microphones near Australia on March 8, 2014, within the time window when the plane disappeared.</p>
<p>The team picked out two weak signals likely produced on that date by two ocean-impacting objects. The researchers determined, however, that the locations of these impacts were too far away from the course that the plane is believed to have taken. Instead, the impacts may have been produced by small meteorites falling into the sea. Kadri says that if the entire plane had crashed into the ocean, it would have produced a much stronger, clearer signal.</p>
<p>“The fact that there was no strong signature might suggest that at least some parts were detached from the airplane before impacting,” Kadri says. “With better data filtering, we may be able to revisit the Malaysia Airlines mystery and to try to identify other possible signals.”</p>
<p>The paper’s co-authors include researchers from Cardiff University, where Kadri also serves as a lecturer, and Memorial University of Newfoundland.</p>
<p><strong>At the speed of sound</strong></p>
<p>Acoustic-gravity waves are sound waves that are typically produced by high-impact sources such as underwater explosions or surface impacts. These waves can travel hundreds of miles across the deep ocean at the speed of sound before dissipating.</p>
<p>Kadri and his colleagues carried out experiments to see whether objects hitting the water’s surface produced a characteristic pattern in acoustic-gravity waves. They dropped 18 weighted spheres into a large water tank, from various heights and locations, and recorded the resulting acoustic-gravity waves using a hydrophone.</p>
<p>For each impact, the team observed a similar sound wave profile, consisting of three main parts.</p>
<p>“We found there was a very special structure to these impacting objects,” Kadri says. “The first part seems to be the initial impact itself, followed by the second part — as the object enters the water, it traps some air, which eventually rises back to the surface. The last part seems to be secondary waves that impact the bottom of the tank, before reflecting back up.”</p>
<p>The researchers then developed a mathematical model to relate a particular pattern of acoustic-gravity waves to certain properties of its source, such as its original location, time of occurrence, duration, and speed of impact. They found the model accurately calculated the location and time of two recent earthquakes, using acoustic-gravity wave data from nearby hydrophones.</p>
<p>After verifying the model, the team used it to try and locate evidence of the Malaysia Airlines plane crash. The researchers first looked through data from the Comprehensive Nuclear-Test-Ban Treaty Organization’s three hydrophone stations off the coast of western Australia. The data were collected within an 18-hour time window on March 8, 2014.</p>
<p><strong>A mystery continues</strong></p>
<p>The researchers focused on a two-hour period, between 0:00 and 02:00 UTC, during which the plane is believed to have crashed in the southern Indian Ocean. They identified two “remarkably weak” signals, according to Kadri, each with an acoustic-gravity wave pattern similar to those created by impacting objects.</p>
<p>The first event was recorded only a few minutes after the last transmission time between the aircraft and a monitoring satellite. However, the researchers determined the event occurred about 500 kilometers away from the plane’s last known location. The aircraft would have had to fly faster than 3,300 kilometers per hour for nine minutes — an unlikely scenario.</p>
<p>The second event occurred closer to the plane’s presumed path, about an hour after the plane’s last transmission. While the signal is too weak to confidently decipher, the researchers suggest that it could have been produced by a “delayed implosion or impact with the sea floor.”</p>
<p>Given the timing and locations of the two events, however, it is more likely that they were generated by falling meteorites. As the team notes in their paper, between 18,000 and 84,000 meteorites bigger than 10 grams fall to Earth each year. If the two signals were indeed produced by meteorites, they would have been relatively large in mass.</p>
<p>The team has submitted its analysis to the Australian Transport Safety Bureau, which led the investigation into flight 370. In the meantime, the researchers plan to apply their method to locate and study other acoustic-gravity wave sources.</p>
<p>“We have a method that we can use to identify general events in the ocean, and we can do that to a high degree of accuracy from a single hydrophone station,” Kadri says. “These events can be an earthquake, an underwater explosion, a falling meteorite, or a plane crash.”</p>
Acoustic-gravity waves are sound waves that are typically produced by high-impact sources such as underwater explosions or surface impacts. Usama Kadri and his colleagues carried out experiments to see whether objects hitting a water’s surface produced a characteristic pattern in acoustic-gravity waves.
Image: Jose-Luis Olivares/MITFluid dynamics, Mathematics, Oceanography and ocean engineering, Physics, Research, School of Science, WaterTechnique spots warning signs of extreme eventshttps://news.mit.edu/2017/technique-spots-warning-signs-climate-aircraft-oceans-0922
Method may help predict hotspots of instability affecting climate, aircraft performance, and ocean circulation.Fri, 22 Sep 2017 13:59:59 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2017/technique-spots-warning-signs-climate-aircraft-oceans-0922<p>Many extreme events — from a rogue wave that rises up from calm waters, to an &nbsp;instability inside a gas turbine, to the sudden extinction of a previously hardy wildlife species — seem to occur without warning. It’s often impossible to predict when such bursts of instability will strike, particularly in systems with a complex and ever-changing mix of players and pieces.</p>
<p>Now engineers at MIT have devised a framework for identifying key patterns that precede an extreme event. The framework can be applied to a wide range of complicated, multidimensional systems to pick out the warning signs that are most likely to occur in the real world.</p>
<p>“Currently there is no method to explain when these extreme events occur,” says Themistoklis Sapsis, associate professor of mechanical and ocean engineering at MIT. “We have applied this framework to turbulent fluid flows, which are the Holy Grail of extreme events. They’re encountered in climate dynamics in the form of extreme rainfall, in engineering fluid flows such as stresses around an airfoil, and acoustic instabilities inside gas turbines. If we can predict the occurrence of these extreme events, hopefully we can apply some control strategies to avoid them.”</p>
<p>Sapsis and MIT postdoc Mohammad Farazmand have published their results today in the journal <em>Science Advances. </em></p>
<p><strong>Looking past exotic warnings</strong></p>
<p>In predicting extreme events in complex systems, scientists have typically attempted to solve sets of dynamical equations — incredibly complex mathematical formulas that, once solved, can predict the state of a complex system over time.</p>
<p>Researchers can plug into such equations a set of initial conditions, or values for certain variables, and solve the equations under those conditions. If the result yields a state that is considered an extreme event in the system, scientists can conclude that those initial conditions must be a precursor, or warning sign.</p>
<p>Dynamical equations are formulated based on a system’s underlying physics. But Sapsis says that the physics governing many complex systems are often not well-understood and they contain important model errors. Relying on these equations to predict the state of such systems would therefore be unrealistic.</p>
<p>Even in systems where the physics are well-characterized, he says there is a huge number of initial conditions one could plug into associated equations, to yield an equally huge number of possible outcomes. What’s more, the equations, based on theory, might successfully identify an enormous number of precursors for extreme events, but those precursors, or initial states, might not all occur in the real world.</p>
<p>“If we just blindly take the equations and start looking for initial states that evolve to extreme events, there is a high probability we will end up with initial states that are very exotic, meaning they will never ever occur for any practical situation,” Sapsis says. “So equations contain more information than we really need.”</p>
<p>Aside from equations, scientists have also looked through available data on real-world systems to pick out characteristic warning patterns. But by their nature, extreme events occur only rarely, and Sapsis says if one were to rely solely on data, they would need an enormous amount of data, over a long period of time, to be able to identify precursors with any certainty.</p>
<p><strong>Searching for hotspots</strong></p>
<p>The researchers instead developed a general framework, in the form of a computer algorithm, that combines both equations and available data to identify the precursors of extreme events that are most likely to occur in the real world.</p>
<p>“We are looking at the equations for possible states that have very high growth rates and become extreme events, but they are also consistent with data, telling us whether this state has any likelihood of occurring, or if it’s something so exotic that, yes, it will lead to an extreme event, but the probability of it occurring is basically zero,” Sapsis says.</p>
<p>In this way, the framework acts as a sort of sieve, capturing only those precursors that one would actually see in a real-world system.</p>
<p>Sapsis and Farazmand tested their approach on a model of turbulent fluid flow — a prototype system of fluid dynamics that describes a chaotic fluid, such as a plume of cigarette smoke, the airflow around a jet engine, ocean and atmospheric circulation, and even the flow of blood through heart valves and arteries.</p>
<p>“We used the equations describing the system, as well as some basic properties of the system, expressed through data obtained from a small number of numerical simulations, and we came up with precursors which are characteristic signals, telling us before the extreme event starts to develop, that there is something coming up,” Sapsis explains.</p>
<p>They then performed a simulation of a turbulent fluid flow and looked for the precursors that their method predicted. They found the precursors developed into extreme events between 75 and 99 percent of the time, depending on the complexity of the fluid flow they were simulating.</p>
<p>Sapsis says the framework is generalizable enough to apply to a wide range of systems in which extreme events may occur. He plans to apply the technique to scenarios in which fluid flows against a boundary or wall. Examples, he says, are air flows around jet planes, and ocean currents against oil risers.</p>
<p>“This happens in random places around the world, and the question is being able to predict where these vortices or hotspots of extreme events will occur,” Sapsis says. “If you can predict where these things occur, maybe you can develop some control techniques to suppress them.”</p>
<p>This research was supported, in part, by the Office of Naval Research, the Air Force Office of Scientific Research, and the Army Research Office.</p>
Engineers at MIT have devised a framework for identifying key patterns that precede an extreme event.Computer modeling, Fluid dynamics, Mechanical engineering, Oceanography and ocean engineering, Climate, Evolution, Oil and gas, Research, School of Engineering, WeatherFor the love of ice: Journeys to the remote and inhospitablehttps://news.mit.edu/2017/glaciologist-alison-criscitiello-seeks-out-ice-cores-for-science-0823
Alison Criscitiello PhD &#039;14 seeks ice cores in inhospitable locations, sometimes camping on ice sheets and sleeping with a shotgun in case of bear attacks. Wed, 23 Aug 2017 16:00:00 -0400Kate Repantis | MIT Alumni Associationhttps://news.mit.edu/2017/glaciologist-alison-criscitiello-seeks-out-ice-cores-for-science-0823<p>Ice has always been fascinating to Alison Criscitiello PhD '14.</p>
<p>“I had a science teacher who did a short unit on glaciers … I couldn’t believe they were real,” she says. That classroom encounter when she was in eight grade in Winchester, Massachusetts,&nbsp;had a lasting impact.</p>
<p>Criscitiello went on to earn MIT’s first PhD in glaciology, and now she&nbsp;is an adjunct assistant professor of glaciology at the University of Calgary in Canada. She studies the history of sea ice and polar marine environments, primarily by drilling ice cores on land-based ice sheets and ice caps in both the Arctic and Antarctic. In March, Criscitiello became the technical director of the newly-created Canadian Ice Core Archive at the University of Alberta, where scientists will have access to 1.7 kilometers of core samples.</p>
<p>“The very northernmost reaches of the Canadian High Arctic are incredibly understudied and under­sampled,” says Criscitiello. To reach remote sites, she often must take several small prop plane flights and then ski in to the destination. On trips to such places as West Antarctica and Greenland, she has had to camp on ice sheets; in Greenland, she’s even slept with a shotgun in case of polar bear attacks.</p>
<p>In a 2014 <a href="http://ladyparagons.com/2014/10/women-in-stem-podcast-episode-12-alison-criscitiello/?doing_wp_cron=1496426605.6988620758056640625000" rel="noopener" target="_blank">Lady Paragons Women in STEM podcast</a>, Criscitiello said she does not mind the hardships:&nbsp;“For me, there is really nothing else in the world that compares to that feeling of being somewhere incredibly remote and frozen, even if it’s inhospitable.”</p>
<p>Her 40-day winter ski traverse with Rebecca ­Haspel and Kate Harris&nbsp;SM ’10&nbsp;through the Pamir Mountains of Central Asia&nbsp;in 2015 is the subject of the new documentary&nbsp;"Borderski." In it, the women travel&nbsp;along Tajikistan’s border with Kyrgyzstan, China, and Afghanistan to bring attention to conservation of the area’s migratory wildlife. The three reunited this winter to bike a 1,450-kilometer ice road that connects remote communities in northern Canada.</p>
<p>Criscitiello has also led the first all-women’s summit of Pinnacle Peak in the Indian Himalayas. Recent expeditions have included summiting Mount Logan, Canada’s highest peak, and the first all-female ascents of mixed routes off Alaska’s Pika Glacier.</p>
<p>In 2016, Criscitiello cofounded Girls on Ice Canada, a nonprofit wilderness and science education program that gives First Nations girls free opportunities to experience scientific mountain expeditions. In her free time, she blows glass and plays the mandolin.</p>
<p>Why the mandolin? “It’s very portable,” she says, “and I can take it on trips.”</p>
<p><em>This article originally appeared in the <a href="https://www.technologyreview.com/mit-news/2017/07/" target="_blank">July/August&nbsp;2017 issue</a></em><em>&nbsp;of&nbsp;</em>MIT Technology Review<em>&nbsp;magazine.</em></p>
Alison Criscitiello PhD '14 summits Mount Logan, Canada’s highest mountain, in May 2016 after ice coring nearby in the Yukon Territory.Photo: Vincent LarochelleEAPS, School of Science, Oceanography and ocean engineering, Alumni/ae, GeologySix from MIT awarded 2017 Fulbright grantshttps://news.mit.edu/2017/six-from-mit-awarded-fulbright-student-grants-0809
Grantees will spend the 2017-2018 academic year conducting research abroad.Wed, 09 Aug 2017 13:20:01 -0400Julia Mongo | Office of Distinguished Fellowshipshttps://news.mit.edu/2017/six-from-mit-awarded-fulbright-student-grants-0809<p>Three MIT graduate students and three recent alumni have been awarded Fulbright U.S. Student Program grants to conduct independent research projects overseas during the coming academic year. In addition, a graduate student alumnus was named a Fulbright Finalist but declined the award.</p>
<p>The 2017-2018 Fulbright Students from MIT will engage in research projects in Germany, Austria, China, New Zealand, Mexico, and Poland.</p>
<p>The Fulbright Program is sponsored by the U.S. Department of State’s Bureau of Educational and Cultural Affairs and operates in over 160 countries worldwide. It is designed to increase mutual understanding between the people of the United States and the people of other countries. Recipients of Fulbright awards are selected on the basis of academic and professional achievement as well as record of service and leadership potential in their respective fields. The MIT winners are:</p>
<p><strong>James Deng '17</strong> graduated from MIT this spring with a BS in chemistry. During his Fulbright year in Germany, he will do research on epigenetics at the Ludwig Maximillian University of Munich. Deng will be investigating the interactions and regulation of TET proteins, which are associated with cancer and other diseases.</p>
<p><strong>Jesse Feiman</strong> is an art history doctoral student in the History Theory and Criticism program within the School of Architecture and Planning. He will be spending his Fulbright year in Austria conducting archival research on the taxonomy system developed by the 18th century Viennese artist Adam von Bartsch. &nbsp;</p>
<p><strong>Jessica Gordon</strong> is a doctoral student in the Department of Urban Studies and Planning. Her Fulbright research in China will examine how governmental policies affect climate change adaptation. She will be conducting her research in Inner Mongolia, Jiangxi, and Guizhou provinces.</p>
<p><strong>Jorlyn Le Garrec '17</strong> graduated this spring with a BS in mechanical and ocean engineering. As a Fulbright Student in New Zealand, she will pursue a research-based mechanical engineering master’s degree through the University of Auckland. Le Garrec’s research focuses on underwater robotics.</p>
<p><strong>Albert Lopez</strong> is an architectural history doctoral student in the History Theory and Criticism program within the School of Architecture and Planning. Lopez will be based in Mexico City, where he will use his Fulbright grant to investigate architects’ contributions to Mexican political society and the discourses of integration during the 1940s-1950s.&nbsp;</p>
<p><strong>Jiwon Victoria Park '17</strong> graduated this spring with a BS in chemistry. She will be traveling to Poland to conduct research in organometallic chemistry at the Warsaw University of Technology. Park’s research has potential applications for drug delivery and electronic devices.</p>
Top row (l-r): James Deng, Jesse Feiman, Jessica Gordon. Bottom row: Jorlyn Le Garrec, Albert Lopez, Jiwon Victoria Park. Awards, honors and fellowships, Students, Undergraduate, Graduate, postdoctoral, Alumni/ae, Urban studies and planning, Mechanical engineering, Oceanography and ocean engineering, Chemistry, School of Architecture and Planning, School of Engineering, School of Science, Global, International initiativesPhytoplankton and chipshttps://news.mit.edu/2017/phytoplankton-and-chips-support-for-darwin-project-data-processing-0804
Simons Foundation supports enhanced computer infrastructure for MIT&#039;s Darwin Project, which focuses on marine microbes and microbial communities. Fri, 04 Aug 2017 18:10:01 -0400Helen Hill | EAPShttps://news.mit.edu/2017/phytoplankton-and-chips-support-for-darwin-project-data-processing-0804<p>Microbes mediate the global marine cycles of elements, modulating atmospheric carbon dioxide and helping to maintain the oxygen we all breathe, yet there is much about them scientists still don’t understand. Now, an award from the Simons Foundation will give researchers from MIT's <a href="http://darwinproject.mit.edu/" target="_blank">Darwin Project</a> access to bigger, better computing resources to model these communities and probe how they work.</p>
<p>The simulations of plankton populations made by Darwin Project researchers have become increasingly computationally demanding. MIT Professor Michael "<a href="http://eapsweb.mit.edu/people/mick" target="_blank">Mick" Follows</a>&nbsp;and Principal Research Engineer <a href="https://eapsweb.mit.edu/people/cnh">Christopher Hill</a>, both affiliates of the Darwin Project, were therefore delighted to learn of their recent Simons Foundation award, providing them with enhanced compute infrastructure to help execute the simulations of ocean circulation, biogeochemical cycles, and microbial population dynamics that are the bread and butter of their research.</p>
<p>The Darwin Project,&nbsp;an alliance between oceanographers and microbiologists in the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS) and the&nbsp;<a href="https://cee.mit.edu/research/#Parsons" target="_blank">Parsons Lab</a> in the MIT Department of Civil and Environmental Engineering, was conceived as an initiative to “advance the development and application of novel models of marine microbes and microbial communities, identifying the relationships of individuals and communities to their environment, connecting cellular-scale processes to global microbial community structure"&nbsp;with the goal of coupling “state of the art physical models of global ocean circulation with biogeochemistry and genome-informed models of microbial processes."</p>
<p>In response to increases in model complexity and resolution over the course of past decade since the project’s inception in 2007, computational demands have ballooned. Increased fidelity and algorithmic sophistication in both biological and fluid dynamical component models and forays into new statistical analysis approaches, leveraging big-data innovations to analyze the simulations and field data, have grown inexorably.</p>
<p>"The award allows us to grow our in-house computational and data infrastructure to accelerate and facilitate these new modeling capabilities," says Hill, who specializes in Earth and planetary computational science.</p>
<p>The boost in computational infrastructure the award provides for will advance several linked areas of research, including the capacity to model marine microbial systems in more detail, enhanced fidelity of the modeled fluid dynamical environment, support for state of the art data analytics including machine learning techniques, and accelerating and extending genomic data processing capabilities.</p>
<p>High diversity is a ubiquitous aspect of marine microbial communities that is not fully understood and, to date, is rarely resolved in simulations. Darwin Project researchers have broken new ground and continue to push the envelope in modeling in this area: In addition to resolving a much larger number of phenotypes and interactions than has typically been attempted by other investigators, the Darwin Project team has also been increasing the fidelity of the underlying physiological sub-models which define traits and trade-offs.</p>
<p>"One thing we are doing is implementing simplified metabolic models which resolve additional constraints [electron and energy conservation] and higher fidelity [dynamic representations of macro-molecular and elemental composition]," says Fellows. "These advances require more state variables per phenotype. We have also an explicit radiative transfer model that allows us to better exploit satellite remote sensing data but both come at a greater computational expense.” Darwin researchers are also expanding their models to resolve not only phototrophic and grazer communities in the surface ocean, but to include heterotrophic&nbsp;and chemo-autotrophic populations throughout the water column.</p>
<p>Follows and Hill believe these advances will provide better fidelity to real world observations, a more dynamic and fundamental description of marine microbial communities and biogeochemical cycles, and the potential to examine the underlying drivers and significance of diversity in the system.</p>
<p>"Much of the biological action in the surface ocean occurs at scales currently unresolved in most biogeochemical simulations,” Follows explains. “Numerical models and recent observations show that the sub-mesoscale motions in the ocean have a profound impact on the supply of resources to the surface and the dispersal and communication between different populations. The integral impact of this, and how to properly parameterize it, is not yet clear, but one approach, that is within reach, is to resolve these scales of motion nested within global simulations,"</p>
<p>Hill and Follows hope such advances will allow them to examine both local and regionally integrated effects of fine-scale physical drivers. "We have already completed a full annual cycle numerical simulation that resolves physical processes down to kilometer scales globally," says Hill. “Such simulations provide a basis for driving targeted modeling of, for example, the role of fronts that may involve fully non-hydrostatic dynamics and that could help explain in-situ measurements that suggest enhanced growth rates under such conditions.” Such work is strongly complementary to another Simons Foundation sponsored project, the Simons Collaboration on Ocean Processes and Ecology (SCOPE). As an initiative to&nbsp;advance our understanding of the biology, ecology, and biogeochemistry of microbial processes that dominate Earth’s largest biome — the global ocean — SCOPE seeks to measure, model, and conduct experiments at a model ecosystem site located 100 km north of the Hawaiian island of Oahu that is representative of a large portion of the North Pacific Ocean.</p>
<p>The team has also already implemented algorithms to enable explicit modeling of the relevant fluid dynamics, but here too, the approaches are computationally demanding. "The improved facilities this award provides will enable these extremely demanding experiments to proceed," says Follows.</p>
<p>Enhanced computer resources will also allow Darwin Project researchers to more effectively utilize data analytics. "We are adopting multiple statistical approaches for classifying fluid dynamical and ecosystem features in observations and in simulations which we plan to apply to biogeochemical problems," says Hill.&nbsp;“One current direction, which employs random forest classification to identify features corresponding to training sets, is showing particular promise for objectively quantifying links between biogeochemical event occurrence and physical environment phenomena.”</p>
<p>Not only will&nbsp;these methods provide useful analysis tools for their simulations, the pair also see them bridging to real world interpretations of, for example, metagenomics surveys in the ocean. Follows and Hill see this direction as a route by which to bring simulations and observations closer in new and meaningful ways. The growth in computational infrastructure the Simons award allows for, creates the potential for making much larger queries across more realistic datasets.</p>
<p>The Darwin Project is part of a long and fruitful collaboration with Institute Professor <a href="http://chisholmlab.mit.edu/" target="_blank">Sallie "Penny" Chisholm</a> of MIT’s Department of Civil and Environmental Engineering. Steady growth in available large-scale metagenomic and single-cell genomic data resulting from genetics data activities in the Chisholm Lab are also driving additional computational processing resource needs.</p>
<p>With the new Simons-supported enhancements in computational infrastructure, Darwin Project collaborators in the Chisholm Lab will be able to tackle assembly from larger metagenomic libraries and single-cell genome phylogenies using maximum likelihood and/or Bayesian algorithms. Currently, some large metagenomics assembly activities require compute resources with more memory than this team has readily had available. "Single-cell genome phylogeny activities are computationally demanding and require dedicating compute resources for weeks or months at a time, Hill explains. “This creates a bottleneck for other work. To accelerate work in these areas additional compute resources, some with larger memory than current resources and some with GPU accelerators are going to be hugely beneficial. The new systems will permit larger metagenomics library assembly than is currently possible."</p>
Image: EAPSGrants, Industry, Oceanography and ocean engineering, Ocean science, Microbes, Computer science and technology, Analytics, Computer modeling, Climate, EAPS, Earth and atmospheric sciences, Environment, Civil and environmental engineering, School of Science, School of EngineeringUnderstanding tropical rainfallhttps://news.mit.edu/2017/understanding-tropical-rainfall-0728
Study finds ocean circulation, coupled with trade wind changes, efficiently limits shifting of tropical rainfall patterns.Fri, 28 Jul 2017 18:05:01 -0400Lauren Hinkel | Oceans at MIThttps://news.mit.edu/2017/understanding-tropical-rainfall-0728<p>The Intertropical Convergence Zone (<a href="http://en.wikipedia.org/wiki/Intertropical_Convergence_Zone" target="_blank">ITCZ</a>), also known as the doldrums, is one of the dramatic features of Earth’s climate system. Prominent enough to be seen from space, the ITCZ appears in satellite images as a band of bright clouds around the tropics. Here, moist warm air accumulates in this atmospheric region near the equator, where the ocean and atmosphere heavily interact. Intense solar radiation and calm, warm ocean waters produce an area of high humidity, ascending air, and rainfall, which is fed by converging trade winds from the Northern and Southern Hemispheres. The convected air forms clusters of thunderstorms characteristic of the ITCZ, releasing heat before moving away from the ITCZ — toward the poles — cooling and descending in the subtropics. This circulation completes the&nbsp;<a href="http://www.merriam-webster.com/dictionary/Hadley%20cell" target="_blank">Hadley cells</a>&nbsp;of the ITCZ, which play an important role in balancing Earth’s energy budget — transporting energy between the hemispheres and away from the equator.</p>
<p>However, the position of the ITCZ isn’t static. In order to transport this energy, the ITCZ and Hadley cells shift seasonally between the Northern and Southern Hemispheres, residing in the one that’s most strongly heated from the sun and radiant heat from the Earth’s surface, which on average yearly is the Northern Hemisphere. Accompanying these shifts can be prolonged periods of violent storms or severe drought, which significantly impacts human populations living in its path.</p>
<p>Scientists are therefore keen to understand the climate controls that drive the north-south movement of the ITCZ over the seasonal cycle, as well as on inter-annual to decadal timescales in Earth’s paleoclimatology up through today. Researchers have traditionally approached this issue from the perspective of the atmosphere’s behavior and understanding rainfall, but anecdotal evidence from models with a dynamic ocean has suggested that the ocean’s sensitivity to climate changes could affect the ITCZ’s response. Now,&nbsp;a <a href="http://journals.ametsoc.org/doi/10.1175/JCLI-D-16-0818.1" target="_blank">study</a>&nbsp;from MIT graduate student <a href="http://paocweb.mit.edu/people/brianmg" target="_blank">Brian Green</a>&nbsp;and the Cecil and Ida Green Professor of Oceanography&nbsp;<a href="http://oceans.mit.edu/JohnMarshall/" target="_blank">John Marshall</a>&nbsp;from the Program in Atmospheres, Oceans and Climate in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS) published in the American Meteorological Society’s&nbsp;<em>Journal of Climate</em>, investigates the role that the ocean plays in modulating the ITCZ’s position and appreciates its sensitivity when the Northern Hemisphere is heated. In so doing, the work gives climate scientists a better understanding of what causes changes to tropical rainfall.</p>
<p>“In the past decade or so there’s been a lot of research studying controls on the north-south position of the ITCZ, particularly from this energy balance perspective. ... And this has normally been done in the context of ignoring the adjustment of the ocean circulation — the ocean circulation is either forcing these [ITCZ] shifts or passively responding to changes in the atmosphere above,” Green says. “But we know, particularly in the tropics, that the ocean circulation is very tightly coupled through the trade winds to atmospheric circulation and the ITCZ position, so what we wanted to do was investigate how that ocean circulation might feedback on the energy balance that controls that ITCZ position, and how strong that feedback might be.”</p>
<p>To examine this, Green and Marshall performed experiments in a global climate model with a coupled atmosphere and ocean, and observed how the ocean circulation’s cross-equatorial energy transport and its associated surface energy fluxes affected the ITCZ’s response when they imposed an inter-hemispheric heating contrast. Using a simplified model that omitted landmasses, clouds, and monsoon dynamics, while keeping a fully circulating atmosphere that interacts with radiation highlighted the ocean’s effect while minimized other confounding variables that could mask the results. The addition of north-south ocean ridges, creating a large and small basin, mimicked the behavior of the Earth’s <a href="http://oceans.mit.edu/news/featured-stories/mitnasa-evaluates-efficiency-of-oceans-as-heat-sink-atmospheric-gases-sponge" target="_blank">Atlantic’s meridional overturning circulation</a> and the Pacific Ocean.</p>
<p>Green and Marshall then ran the asymmetrically heated planet simulations in two ocean configurations and compared the ITCZ responses. The first used a stationary “slab ocean,” where the thermal properties were specified so that it mimicked the fully coupled model before perturbation, but was unable to respond to the heating. The second incorporated a dynamic ocean circulation. By forcing the models identically, they could quantify the ocean circulation’s impact on the ITCZ.</p>
<p>“We found in the case where there’s a fully coupled, dynamic ocean, the northward shift of the ITCZ was damped by a factor of four compared to the passive ocean. So that’s hinting that the ocean is one of the leading controls on the position of the ITCZ,” Green says. “It’s a significant damping of the response of the atmosphere, and the reason behind this can just be diagnosed from that energy balance.”</p>
<p>In the dynamic ocean model, they found that when they heat the simulated ocean-covered planet, eddies export some heat into the tropical atmosphere from the extra-tropics, which causes the Hadley cells to respond — the Northern Hemisphere cell to weaken and the Southern Hemisphere cell to strengthen. This transports heat southward through the atmosphere. Concurrently, the ITCZ shifts northward; associated with this are changes in the trade winds — the surface branch of the Hadley cells — and the surface wind stress near the equator. The surface ocean feels this change in winds, which energizes an anomalous ocean circulation and moves water mass southwards across the equator in both hemispheres, carrying heat with it. Once this surface water reaches the extra-tropics, the ocean pumps it downwards where it returns northward across the equator, cooler and at depth. This temperature contrast between the warm surface cross-equatorial flow and the cooler deeper return flow sets the heat transported by the ocean circulation.</p>
<p>“In the slab ocean case, only the atmosphere can move heat across the equator; whereas in our fully coupled case, we see that the ocean is the most strongly compensating component of the system, transporting the majority of the forcing across the equator.” Green says. “So from the atmosphere’s perspective, it doesn’t even feel the full effect of that heating that we’re imposing. And as a result, it has to transport less heat across the equator and shift the ITCZ less.” Green adds that the response of the large basin ocean circulation broadly mimics the Indian Ocean’s yearly average circulation.</p>
<p>Marshall notes that the ability of the wind-driven ocean circulation to damp ITCZ shifts represents a previously unappreciated constraint on the atmosphere’s energy budget: “We showed that the ITCZ cannot move very far away from the equator, even in very ‘extreme’ climates,” indicating that the position of the ITCZ may be much less sensitive to inter-hemispheric heating contrasts than previously thought.”</p>
<p>Green and Marshall are currently expanding upon this work. With the help of&nbsp;<a href="http://web.mit.edu/davidmcg/www/" target="_blank">David McGee</a>, the Kerr-Mcgee Career Development Assistant Professor in EAPS, and postdoc&nbsp;<a href="http://paocweb.mit.edu/people/chamarro" target="_blank">Eduardo Moreno-Chamarro</a>, the pair are applying this to the paleoclimate record during&nbsp;<a href="http://en.wikipedia.org/wiki/Heinrich_event" target="_blank">Heimrich events</a>, when the Earth experiences strong cooling, looking for ITCZ shifts.</p>
<p>They’re also investigating the decomposition of heat and mass transport between the atmosphere and the ocean, as well as between the Earth’s oceans. “The physics that control each of those oceans’ responses are dramatically different, certainly between the Pacific and the Atlantic oceans,” Green says. “Right now, we’re working to understand how the mass transports of the atmosphere and ocean are coupled. While we know that they’re constrained to overturn in the same sense, they’re not actually constrained to transport an identical amount of mass, so you could further enhance or weaken the damping by the ocean circulation by affecting how strongly the mass transports are coupled.”</p>
This image is a combination of cloud data from NOAA’s Geostationary Operational Environmental Satellite (GOES-11) and color land cover classification data. The Intertropical Convergence Zone is the band of bright white clouds that cuts across the center of the Earth. Image: NOAA GOES Project Science Office and NASAOceanography and ocean engineering, EAPS, School of Science, Research, Weather, Climate, Earth and atmospheric sciencesRising temperatures are curbing ocean’s capacity to store carbonhttps://news.mit.edu/2017/rising-temperatures-are-curbing-ocean-capacity-store-carbon-0706
Study finds large amounts of carbon dioxide, equivalent to yearly U.K. emissions, remain in surface waters.Thu, 06 Jul 2017 00:00:00 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2017/rising-temperatures-are-curbing-ocean-capacity-store-carbon-0706<p>If there is anywhere for carbon dioxide to disappear in large quantities from the atmosphere, it is into the Earth’s oceans. There, huge populations of plankton can soak up carbon dioxide from surface waters and gobble it up as a part of photosynthesis, generating energy for their livelihood. When plankton die, they sink thousands of feet, taking with them the carbon that was once in the atmosphere, and stashing it in the deep ocean.</p>
<p>The oceans, therefore, have served as a natural sponge in removing greenhouse gases from the atmosphere, helping to offset the effects of climate change.</p>
<p>But now MIT climate scientists have found that the ocean’s export efficiency, or the fraction of total plankton growth that is sinking to its depths, is decreasing, due mainly to rising global temperatures.</p>
<p>In a new study published in the journal <em>Limnology and Oceanography Letters,</em> the scientists calculate that, over the past 30 years, as temperatures have risen worldwide, the amount of carbon that has been removed and stored in the deep ocean has decreased by 1.5 percent.</p>
<p>To put this number in perspective, each year, about 50 billion tons of new plankton flourish in the surface ocean each year, while about 6 billion tons of dead plankton sink to deeper waters. A 1.5 percent decline in export efficiency would mean that about 100 million tons of extra plankton have remained near the surface each year.</p>
<p>“We figured the amount of carbon that is not sinking out as a result of global temperature change is similar to the total amount of carbon emissions that the United Kingdom pumps into the atmosphere each year,” says first author B.B. Cael, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “If carbon is just standing in the surface ocean, it’s easier for it to end up back in the atmosphere.”</p>
<p>Cael’s co-authors on the paper are Kelsey Bisson of the University of California at Santa Barbara and Mick Follows, an associate professor in EAPS.</p>
<p><strong>Photosynthesizers versus respirers</strong></p>
<p>In 2016, the team first started looking into whether sea surface temperature has an effect on the ocean’s export efficiency. The group’s main research focus is on marine microbes, including interactions between communities, and their effects on and responses to climate change.</p>
<p>In studying export efficiency, the researchers identified two processes in surface ocean microbes that affect the rate at which carbon is drawn down to the deep ocean: Photosynthesizing organisms such as plankton absorb carbon dioxide from surface waters, fixing carbon into their systems; respiring organisms such as bacteria and krill take in oxygen and emit carbon dioxide into the surrounding waters.</p>
<p>Based on the chemistry of photosynthesis and respiration, the researchers realized that the two processes respond differently depending on temperature. Photosynthesizers grow and die relatively faster in colder environments, while respirers are relatively more active in warmer temperatures.</p>
<p>In 2016, the researchers developed a simple model to predict the ocean’s rate of drawing down carbon at given sea surface temperatures. Their results matched with recorded observations of the amount of carbon exported to the deep ocean.</p>
<p>“We had a simple way to describe how we think temperature influences export efficiency, based on this fundamental metabolic theory,” Cael says. “Now, can we use that to see how export efficiency has changed over the time period where we have good temperature records? That’s how we can estimate whether export efficiency is changing as a result of climate change.”</p>
<p><strong>Out to sea</strong></p>
<p>For this new paper, the researchers used the model to estimate the ocean’s export efficiency over the last three decades. Since 1982, satellites, ships, and buoys have made measurements of sea surface temperatures around the world, which scientists have averaged for each measured location and aggregated into publicly available databases.</p>
<p>For this study, the team used temperature measurements from three different databases, taken every month from 1982 to 2014, for locations around the world. The group used the temperature to estimate export efficiency across the global ocean for each month, based on their simple model. They traced the change in export efficiencies across the globe, over the 33-year period during which measurements were available.</p>
<p>They found that, worldwide, the rate at which the ocean draws down carbon has declined by 1 to 2 percent since 1982. Sea surface temperatures have increased during this period.</p>
<p>“People probably expected a decline in export efficiency, but the thing I find interesting is, we have a nice way to try and quantify it,” Cael says. “We’re able to estimate that over last 30 years, export efficiency has declined by 1 or 2 percent, so 1 to 2 percent less of total plankton productivity is making it out of the surface ocean, which is actually a pretty big number.”</p>
<p>Cael says the team’s model could potentially be applied to predict the ocean’s future as a carbon sink, though uncertainty in temperature projections makes this a much more complicated goal.</p>
<p>“How carbon moves around on Earth is fundamental to understanding both Earth’s biosphere and climate, and requires understanding how carbon moves through the ocean,” Cael says. “This [model] is something you could potentially apply to temperature projections, to guess how carbon will move through the Earth in the future.”</p>
<p>This research was supported, in part, by the National Science Foundation, the Simons Foundation, and the Gordon and Betty Moore Foundation.</p>
MIT climate scientists have found that the ocean’s export efficiency, or the fraction of total plankton growth that is sinking to its depths, is decreasing, due mainly to rising global temperatures.Image: MIT NewsClimate change, EAPS, Emissions, Environment, Global Warming, Greenhouse gases, Oceanography and ocean engineering, Research, School of ScienceBatteries that “drink” seawater could power long-range underwater vehicleshttps://news.mit.edu/2017/batteries-drink-seawater-long-range-autonomous-underwater-vehicles-0615
Startup’s novel aluminum batteries increase the range of UUVs tenfold.Thu, 15 Jun 2017 11:00:00 -0400Rob Matheson | MIT News Officehttps://news.mit.edu/2017/batteries-drink-seawater-long-range-autonomous-underwater-vehicles-0615<p>The long range of airborne drones helps them perform critical tasks in the skies. Now MIT spinout Open Water Power (OWP) aims to greatly improve the range of unpiloted underwater vehicles (UUVs), helping them better perform in a range of applications under the sea.</p>
<p>Recently acquired by major tech firm L3 Technologies, OWP has developed a novel aluminum-water power system that’s safer and more durable, and that gives UUVs a tenfold increase in range over traditional lithium-ion batteries used for the same applications.</p>
<p>The power systems could find a wide range of uses, including helping UUVs dive deeper, for longer periods of time, into the ocean’s abyss to explore ship wreckages, map the ocean floor, and conduct research. They could also be used for long-range oil prospecting out at sea and various military applications.</p>
<p>With the acquisition, OWP now aims to ramp up development of its power systems, not just for UUVs, but also for various ocean-floor monitoring systems, sonar buoy systems, and other marine-research devices.</p>
<p>OWP is currently working with the U.S. Navy to replace batteries in acoustic sensors designed to detect enemy submarines. This summer, the startup will launch a pilot with Riptide Autonomous Solutions, which will use the UUVs for underwater surveys. Currently, Riptide’s UUVs travel roughly 100 nautical miles in one go, but the company hopes OWP can increase that distance to 1,000 nautical miles.</p>
<p>“Everything people want to do underwater should get a lot easier,” says co-inventor <a href="http://news.mit.edu/2011/student-profile-mckay">Ian Salmon McKay</a> ’12, SM ’13, who co-founded OWP with fellow mechanical engineering graduate Thomas Milnes PhD ’13 and <a href="http://news.mit.edu/2015/student-profile-ruaridh-macdonald-0902">Ruaridh Macdonald</a> '12, SM '14, who will earn his PhD in nuclear engineering this year. “We’re off to conquer the oceans.”</p>
<p><strong>“Drinking” sea water for power</strong></p>
<p>Most UUVs use lithium-based batteries, which have several issues. They’re known to catch fire, for one thing, so UUV-sized batteries are generally not shippable by air. Also, their energy density is limited, meaning expensive service ships chaperone UUVs to sea, recharging the batteries as necessary. And the batteries need to be encased in expensive metal pressure vessels. In short, they’re rather short-lived and unsafe.</p>
<p>In contrast, OWP’s power system is safer, cheaper, and longer-lasting. It consists of a alloyed aluminum, a cathode alloyed with a combination of elements (primarily nickel), and an alkaline electrolyte that’s positioned between the electrodes.</p>
<p>When a UUV equipped with the power system is placed in the ocean, sea water is pulled into the battery, and is split at the cathode into hydroxide anions and hydrogen gas. The hydroxide anions interact with the aluminum anode, creating aluminum hydroxide and releasing electrons. Those electrons travel back toward the cathode, donating energy to a circuit along the way to begin the cycle anew. Both the aluminum hydroxide and hydrogen gas are jettisoned as harmless waste.</p>
<p>Components are only activated when flooded with water. Once the aluminum anode corrodes, it can be replaced at low cost.</p>
<p>Think of the power system as type of underwater engine, where water is the oxidizer feeding the chemical reactions, instead of the air used by car engines, McKay says. “Our power system can drink sea water and discard waste products,” he says. “But that exhaust is not harmful, compared to exhaust of terrestrial engines.”</p>
<p>With the aluminum-based power system, UUVs can launch from shore and don’t need service ships, opening up new opportunities and dropping costs. With oil prospecting, for example, UUVs currently used to explore the Gulf of Mexico need to hug the shores, covering only a few pipeline assets. OWP-powered UUVs could cover hundreds of miles and return before needing a new power system, covering all available pipeline assets.</p>
<p>Consider also the Malaysian Airlines crash in 2014, where UUVs were recruited to search areas that were infeasible for equipment on the other vessels, McKay says. “In looking for the debris, a sizeable amount of the power budget for missions like that is used descending to depth and ascending back to the surface, so their working time on the sea floor is very limited,” he says. “Our power system will improve on that.”</p>
<p><strong>Nailing the design</strong></p>
<p>The OWP technology started as the co-founders’ side project, which was modified throughout two MIT classes and a lab. In 2011, McKay joined 2.013/2.014 (Engineering System Design/Development) taught by MIT professor of mechanical engineering Douglas Hart, a seasoned hardware entrepreneur who co-founded <a href="http://news.mit.edu/2013/brontes-technologies-0821">Brontes Technologies</a> and Lantos Technologies. Milnes, who was previously a systems engineer at Brontes and co-founded <a href="http://news.mit.edu/2014/3-d-scanning-with-your-smartphone-0131">Viztu Technologies</a>, was Hart’s teaching assistant.</p>
<p>The class was charged with developing an alternate power source for UUVs. McKay gambled on an energy-dense but challenging element: aluminum. One major challenge with aluminum batteries is that certain chemical issues make it difficult to donate electrons to a circuit. Additionally, the product of the reactions, the aluminum hydroxide, sticks to the electrode’s surface, inhibiting further reaction. Continuing the work in 10.625 (Electrochemical Energy Conversion and Storage), taught by materials science Professor Yang Shao-Horn, the W. M. Keck Professor of Energy, McKay was able to overcome the first challenge by making a gallium-rich alloyed aluminum anode that successfully donated electrons, but it corroded very quickly.</p>
<p>Seeing potential in the battery, Milnes joined McKay in further developing the battery as a side project. The two briefly moved operations to the lab of Evelyn Wang, the Gail E. Kendall Professor of Mechanical Engineering. There, they began developing electrolytes and alloys that inhibit parasitic corrosion processes and prevent that aluminum hydroxide layer from forming on the anode.</p>
<p>Setting up shop at Greentown Labs in Somerville, Massachusetts, in 2013 — where the company still operates with about 10 employees — OWP further refined the power system’s design. Today, that power system uses a pump to circulate the electrolyte, scooping up unwanted aluminum hydroxide on the anode and dumping it onto a custom precipitation trap. When saturated, the traps with the waste are ejected and replaced automatically. The electrolyte prevents marine organisms from growing inside the power system.</p>
<p>Now OWP’s chief science officer, McKay says the startup owes much of its success to MIT’s atmosphere of innovation, where many of his professors readily offered technical and entrepreneurial advice and allowed him to work on extracurricular projects.</p>
<p>“It takes a village,” McKay says. “Those classes and that lab are where the idea took shape. People at MIT were doing strong science for science’s sake, but everyone was keenly aware of the possibility of bringing technologies to market. People were always having those great ‘What if?’ conversations — I probably had three to four different startup ideas in various stages of gestation at any given time, and so did all my friends. It was an environment that encouraged the playful exchange of ideas, and encouraged people to take on side projects with real prizes in mind.”</p>
Open Water Power’s battery that "drinks" in sea water to operate is safer and cheaper, and provides a tenfold increase in range, over traditional lithium-ion batteries used for unpiloted underwater vehicles. The power system consists of an alloyed aluminum anode, an alloyed cathode, and an alkaline electrolyte positioned between the electrodes. Components are only activated when flooded with water. Once the aluminum anode corrodes, it can be replaced at low cost.
Courtesy of Open Water PowerSchool of Engineering, Mechanical engineering, Innovation and Entrepreneurship (I&E), Startups, Alumni/ae, Oceanography and ocean engineering, Drones, Autonomous vehicles, Security studies and military, Oil and gas, Batteries, Energy, Energy storageHigh-speed images capture archer fish’s rocket-like launchhttps://news.mit.edu/2017/high-speed-images-capture-archer-fish-launch-0419
Insights into the hydrodynamics of the move may improve underwater vehicle design. Wed, 19 Apr 2017 17:59:59 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2017/high-speed-images-capture-archer-fish-launch-0419<p>The archer fish is arguably the ninja of the aquatic world, known for its stealth-like, arrow-straight aim while shooting down unsuspecting prey. Once the fish has sighted its target, it can spit jets of water to dislodge insects from overhanging leaves, making them topple into the water.</p>
<p>But once an insect is shot down, it becomes fair game for any passing predator, and the archer fish is not necessarily the first to catch the fallen quarry. That’s when the fish’s other equally impressive, though less-studied, prey-capture strategy can be an advantage. In addition to spit-shooting, an archer fish can launch itself from a near standstill, out of the water to a height of more than two times its body length. In this way, it can catch an insect in midair, ensuring that no other competitor steals its prey.</p>
<p>Now MIT engineers have detailed the hydrodynamics of the archer fish’s rocket-like jumping behavior in a paper published in the <em>Journal of Experimental Biology. </em></p>
<p>“Unlike, say, a shark that comes barreling up from the bottom to catch its prey, an archer fish’s initial momentum is zero,” says Alexandra Techet, associate professor of mechanical engineering at MIT. “All that force has to be created close to the surface, at a near standstill. That’s what makes this fish really interesting to study and completely different than your traditional leaping and jumping problem.”</p>
<p>Techet says understanding how the archer fish propels itself out of the water can help guide the design of surfacing underwater vehicles.</p>
<p>“It would be nice to see a way to create a vehicle that could, say, spyhop from water to air, over a short duration,” Techet says, referring to the way some whales raise their heads vertically out of the water. “Results from this [study] might help us to come up with theories for how you might connect biology to mechanics.”</p>
<p>Techet’s co-authors on the study are lead author and former graduate student Anna Shih and graduate student Leah Mendelson.</p>
<p><strong>Training a fish to jump</strong></p>
<p>Archer fish are typically found in mangrove swamps, river mouths, and upstream brackish and freshwater regions in Southeast Asia. The team obtained 10 small archer fish from a local aquarium store and housed them in a 55-gallon “home tank” filled with brackish water. They trained the fish to jump by suspending freeze-dried shrimp above the water’s surface and temporarily withdrawing the food if the fish spit. After about a month of training, five of the 10 fish were trained to reliably jump for their food.</p>
<p>The researchers then set up an experimental 10-gallon tank, which they filled with water and seeded with polyamide particles — tiny beads that are virtually invisible to the naked eye and neutrally buoyant, meaning their density is equal to that of the surrounding water. Techet and her colleagues placed a laser below the tank to illuminate the beads with infrared light, a technique known as Particle Image Velocimetry (PIV). A high-speed camera, placed in front of the tank, captured the motions of the beads and therefore the direction and velocity of any eddies and vortices produced in the water.</p>
<p>“We can track from one time to another where those particles have moved, and can use image processing to get velocity vectors,” Techet explains. “Ideally that will give us an idea of how much thrust or energy the fish can generate to get itself up to some height.”</p>
<p>In separate trials, the team placed each of the five fish into the experimental tank and suspended above it a piece of freeze-dried shrimp at varying heights, from one-fourth to more than two times a fish’s body length. The high-speed camera recorded 98 jumping sequences, averaging about 16 to 24 jumps per fish.</p>
<p><strong>To catch a prey</strong></p>
<p>Frame by frame, the team analyzed each fish’s body motions while jumping, as well as the direction and velocity of the particles displaced by the fish’s movements.</p>
<p>From the motions of each fish, Techet and her team identified three general phases in jumping behavior: hovering, thrust production, and gliding.</p>
<p>In the first phase, the fish hovers just under the water’s surface, with its snout positioned at the surface to spot any overhanging prey. By alternately flapping its pectoral fins and waving its caudal fin, the fish is able to hover in place as it looks for prey.</p>
<p>The second phase begins as the fish prepares to produce upward thrust by raising its pectoral and pelvic fins while simultaneously beating its tail back and forth, until the fish produces enough thrust to launch itself out of the water.</p>
<p>During the final gliding phase, the fish essentially glides through the air and up to the bait, accelerating only due to gravity or to changes in its posture, and not from any further thrust production.</p>
<p><strong>“No running start”</strong></p>
<p>Interestingly, the team noted that the number of tail beats each fish produced was related to the height of the bait: The higher the bait, the more times the fish beat its tail, likely to produce enough thrust to reach the food. Mendelson points out that this is an impressive feat, seeing as the fish, stationed right at the water’s surface, has a limited amount of space in which to build up the adequate amount of thrust.</p>
<p>“How do you accelerate when the most critical thing that’s in scarce supply is the space you have to do it in?” Mendelson says. “There’s no running start. And to me that’s one of the biggest takeaways.”</p>
<p>Remarkably, the fish were able to launch themselves to a height as great as 2.5 times their body length. The researchers also tracked the direction and speed of the particles in the tank as the fish propelled itself out of the water, creating eddies in its wake. On average, the maximum velocities during each run ranged from 0.6 to 1.7 meters per second squared.</p>
<p>“The speed they leave the water with is on the order of Olympic swimmer speeds,” Mendelson says. “The record for the 100-meter freestyle record is a little under 50 seconds, so, 2 meters per second. So these fish are almost as fast as an Olympic swimmer, but actually going up rather than horizontal.”</p>
<p>Next, the team plans to set up more cameras around the tank to study the fish’s jumping behavior from a three-dimensional perspective. The current work, based on one camera’s perspective, gives only a two-dimensional view. Techet suspects that, with a more comprehensive picture, they will find that not only the fish’s tail but also its other fins play a role in stabilizing and propelling the fish out of water.</p>
<p>Ultimately, Techet hopes to use what she learns from nature to engineer more agile underwater vehicles.</p>
<p>“Can we understand nature to help us design mechanical systems? What can I learn about these fish that go from a dead start, to jumping out of the water?” Techet says. “Am I going to make a flapping robot that jumps out of the water? Probably not. But the concepts here are ubiquitous between fish, propulsors, and foils in general.”</p>
In addition to spit-shooting, an archer fish, pictured here, can launch itself from a near standstill, out of the water to a height of more than two times its body length. “Unlike, say, a shark that comes barreling up from the bottom to catch its prey, an archer fish’s initial momentum is zero,” says Alexandra Techet, associate professor of mechanical engineering at MIT.
Biomechanics, Fluid dynamics, Mechanical engineering, Oceanography and ocean engineering, Animals, Ecology, Research, School of EngineeringUnderwater mountains help ocean water rise from abysshttps://news.mit.edu/2017/underwater-mountains-turbulence-ocean-circulation-0306
Turbulence from seafloor topography may explain longstanding question about ocean circulation.Mon, 06 Mar 2017 04:59:59 -0500Jennifer Chu | MIT News Officehttps://news.mit.edu/2017/underwater-mountains-turbulence-ocean-circulation-0306<p>At high latitudes, such as near Antarctica and the Arctic Circle, the ocean’s surface waters are cooled by frigid temperatures and become so dense that they sink a few thousand meters into the ocean’s abyss.</p>
<p>Ocean waters are thought to flow along a sort of conveyor belt that transports them between the surface and the deep in a never-ending loop. However, it remains unclear where the deep waters rise to the surface, as they ultimately must. This information would help researchers estimate how long the ocean may store carbon in its deepest regions before returning it to the surface.</p>
<p>Now scientists from MIT, Woods Hole Oceanographic Institution (WHOI), and the University of Southampton in the U.K. have identified a mechanism by which waters may rise from the ocean’s depths to its uppermost layers. Their results are published today in the journal <em>Nature Communications.</em></p>
<p>Through numerical modeling and observations in the Southern Ocean, the team found that topographic features such as seamounts, ridges, and continental margins can trap deep waters from migrating to flatter, calmer parts of the ocean. The underwater chasms and cliffs generate turbulent flows, similar to wind that whips between a city’s skyscrapers. The longer water is trapped among these topographic features, the more it mixes with upper layers of the ocean, swirling its way back toward the surface.</p>
<p>“In the abyssal ocean, you have 4,000-meter sea mountains and very deep troughs, up and down, and these topographic features help create turbulence,” says Raffaele Ferrari, the Cecil and Ida Green Professor of Oceanography in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “What seems to be emerging is that water comes back up from the abyss by spending a lot of time in these places where turbulence is really strong.”</p>
<p>Knowing there are hotspots where deep waters return to the surface may help scientists identify regions where carbon, once absorbed from the atmosphere and stored deep in the ocean, rises and is released back to the atmosphere.</p>
<p>“The general understanding is&nbsp;that abyssal waters take few to several thousand years to resurface,” says lead author and MIT postdoc Ali Mashayek. “If a considerable amount of such upwelling occurs rapidly along sloped boundaries, continental margins, and mid-ocean ridges, then the timescale of recycling of abyssal waters can be shorter.”</p>
<p>Ferrari and Mashayek’s co-authors are Sophia Merrifield, an MIT graduate student; Jim Ledwell and Lou St. Laurent of WHOI; and Alberto Naveira Garabato of the University of Southampton.</p>
<p><strong>The power of 10 light bulbs</strong></p>
<p>In cold polar regions, the amount of water that continually sinks to the deep ocean is estimated to be “about 10<sup>7</sup> cubic meters per second — 50 times the transport of the Amazon River,” Ferrari says.</p>
<p>In 1966, acclaimed oceanographer Walter Munk addressed the puzzle of how all this deep water returns to the surface, proposing that small-scale ocean turbulence may drive heavy, deep water to mix and rise. This turbulence, he posited, takes the form of breaking internal gravity waves that travel between water layers of different densities, below the ocean’s surface.</p>
<p>Munk calculated the mixing power that would have to be generated by breaking internal gravity waves to bring all the ocean’s deep water back up to the surface. The number, Ferrari says, is equivalent to “about 10 incandescent light bulbs per cubic kilometer of the ocean.”</p>
<p>Since then, oceanographers have identified limited areas, such as seamounts and ridges, that create turbulence similar to what Munk theorized.</p>
<p>“But if you summed those few places up, you didn’t seem to come up to the number you needed to bring all that water back up,” Ferrari says.</p>
<p><strong>Making passage</strong></p>
<p>In February 2009, collaborators from WHOI deployed a tracer in the Southern Ocean, about 1,000 miles west of Drake Passage, as part of a project called DIMES (Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean) to analyze the mixing of ocean waters.</p>
<p>“They released a blob of dye, like a drop of milk in a coffee cup, and let the ocean mix it around,” Ferrari says.</p>
<p>Over two years, they sampled the tracer at various stations downstream from where it was released, and found that it experienced very little turbulence, or mixing, in parts of the ocean with few topographic features. However, once the tracer crossed Drake Passage, it encountered seamounts and ridges, and “all of a sudden, it started to spread in the vertical quite fast, at three times the rate predicted by Munk,” Ferrari says.</p>
<p>What was driving this accelerated mixing? To find out, the team, led by Mashayek, developed a numerical model to simulate the Southern Ocean region — no small task, as it was unclear whether such a model could have high enough resolution to reproduce a tracer’s small-scale movements amid a vast volume of seawater.</p>
<p>“I did some preliminary calculations, back of the envelope estimates, and realized we would have just enough resolution to be able to do it,” Mashayek recalls.</p>
<p><strong>A tracer, trapped</strong></p>
<p>The researchers used MIT’s general circulation model — a numerical model designed to study the Earth’s atmosphere, ocean, and climate — as their framework, and programmed into it all the external forces that are known to exist in the Southern Ocean, including wind patterns, solar heating, evaporation, and precipitation. They then worked measurements from the DIMES experiment into the model and extrapolated the turbulence across the entire ocean region, given the underlying topography.</p>
<p>The team then placed a tracer in its model at the same location where the real tracer was released into the Southern Ocean, and observed that, indeed, it spread vertically, at the same rate that the researchers observed in the field, proving that the model was representing the real ocean’s turbulence.</p>
<p>Looking more closely at their simulations, the researchers observed that regions with topography such as seamounts and ridges were essentially trapping the tracer for long periods of time, buffeting and mixing it vertically, before the tracer escaped and drifted through calmer waters.</p>
<p>The researchers believe the turbulence that occurs in these isolated regions over long periods of time may measure up to the total amount of mixing that Munk initially predicted. This mixing process may thus explain how waters in the deep ocean swell back up to the surface.</p>
<p>“Mixing-induced upwelling is&nbsp;globally relevant,” Mashayek says. “If our finding in the Southern Ocean extends to other mixing hotspots around the globe, then it will somewhat reshape our understanding of role of turbulent mixing in ocean overturning circulation. It also has important implications for parameterization of mixing processes in climate models.”</p>
<p>This research was supported, in part, by the National Science Foundation.</p>
A map of a seamount in the Arctic Ocean created by gathering data with a multibeam echo sounder. Researchers have found that such topographic features can trap deep waters and produce turbulence.Image courtesy of National Oceanic and Atmospheric Administration (NOAA)Climate, Climate change, Computer modeling, EAPS, Earth and atmospheric sciences, Fluid dynamics, National Science Foundation (NSF), Oceanography and ocean engineering, Research, School of ScienceNew study sets oxygen-breathing limit for ocean’s hardiest organismshttps://news.mit.edu/2016/oxygen-breathing-limit-ocean-bacteria-1219
Bacteria can survive in marine environments that are almost completely starved of oxygen.Mon, 19 Dec 2016 00:00:02 -0500Jennifer Chu | MIT News Officehttps://news.mit.edu/2016/oxygen-breathing-limit-ocean-bacteria-1219<p>Around the world, wide swaths of open ocean are nearly depleted of oxygen. Not quite dead zones, they are “oxygen minimum zones,” where a confluence of natural processes has led to extremely low concentrations of oxygen.</p>
<p>Only the hardiest of organisms can survive in such severe conditions, and now MIT oceanographers have found that these tough little life-forms — mostly bacteria — have a surprisingly low limit to the amount of oxygen they need to breathe.</p>
<p>In a paper published by the journal <em>Limnology and Oceanography</em>, the team reports that ocean bacteria can survive on oxygen concentrations as low as approximately 1 nanomolar per liter. To put this in perspective, that’s about 1/10,000th the minimum amount of oxygen that most small fish can tolerate and about 1/1,000th the level that scientists previously suspected for marine bacteria.</p>
<p>The researchers have found that below this critical limit, microbes either die off or switch to less common, anaerobic forms of respiration, taking up nitrogen instead of oxygen to breathe.</p>
<p>With climate change, the oceans are projected to undergo a widespread loss of oxygen, potentially increasing the spread of oxygen minimum zones around the world. The MIT team says that knowing the minimum oxygen requirements for ocean bacteria can help scientists better predict how future deoxygenation will change the ocean’s balance of nutrients and the marine ecosystems that depend on them.</p>
<p>“There’s a question, as circulation and oxygen change in the ocean: Are these oxygen minimum zones going to shoal and become more shallow, and decrease the habitat for those fish near the surface?” says Emily Zakem, the paper’s lead author and a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “Knowing this biological control on the process is really necessary to making those sorts of predictions.”</p>
<p>Zakem’s co-author is EAPS Associate Professor Mick Follows.</p>
<p><strong>How low does oxygen go?</strong></p>
<p>Oxygen minimum zones, sometimes referred to as “shadow zones,” are typically found at depths of 200 to 1,000 meters. Interestingly, these oxygen-depleted regions are often located just below a layer of high oxygen fluxes and primary productivity, where fish swimming near the surface are in contact with the oxygen-rich atmosphere. Such areas generate a huge amount of organic matter that sinks to deeper layers of the ocean, where bacteria use oxygen — far less abundant than at the surface — to consume the detritus. Without a source to replenish the oxygen supply at such depths, these zones quickly become depleted.</p>
<p>Other groups have recently measured oxygen concentrations in depleted zones using a highly sensitive instrument and observed, to their surprise, levels as low as a few nanomolar per liter — about 1/1,000th of what many others had previously measured — across hundreds of meters of deep ocean.</p>
<p>Zakem and Follows sought to identify an explanation for such low oxygen concentrations, and looked to bacteria for the answer.</p>
<p>“We’re trying to understand what controls big fluxes in the Earth system, like concentrations of carbon dioxide and oxygen, which set the parameters of life,” Zakem says. “Bacteria are among the organisms on Earth that are integral to setting large-scale nutrient distributions. So we came into this wanting to develop how we think of bacteria at the climate scale.”</p>
<p><strong>Setting a limit</strong></p>
<p>The researchers developed a simple model to simulate how a bacterial cell grows. They focused on particularly resourceful strains that can switch between aerobic, oxygen-breathing respiration, and anaerobic, nonoxygen-based respiration. Zakem and Follows assumed that when oxygen is present, such microbes should use oxygen to breathe, as they would expend less energy to do so. When oxygen concentrations dip below a certain level, bacteria should switch over to other forms of respiration, such as using nitrogen instead of oxygen to fuel their metabolic processes.</p>
<p>The team used the model to identify the critical limit at which this switch occurs. If that critical oxygen concentration is the same as the lowest concentrations recently observed in the ocean, it would suggest that bacteria regulate the ocean’s lowest oxygen zones.</p>
<p>To identify bacteria’s critical oxygen limit, the team included in its model several key parameters that regulate a bacterial population: the size of an individual bacterial cell; the temperature of the surrounding environment; and the turnover rate of the population, or the rate at which cells grow and die. They modeled a single bacterial cell’s oxygen intake with changing parameter values and found that, regardless of the varying conditions, bacteria’s critical limit for oxygen intake centered around vanishingly small values.</p>
<p>“What’s interesting is, we found that across all this parameter space, the critical limit was always centered at about 1 to 10 nanomolar per liter,” Zakem says. “This is the minimum concentration for most of the realistic space you would see in the ocean. This is useful because we now think we have a good handle on how low oxygen gets in the ocean, and [we propose] that bacteria control that process.”</p>
<p><strong>Ocean fertility</strong></p>
<p>Looking forward, Zakem says the team’s simple bacterial model can be folded into global models of atmospheric and ocean circulation. This added nuance, she says, can help scientists better predict how changes to the world’s climate, such as widespread warming and ocean deoxygenation, may affect bacteria.</p>
<p>While they are the smallest organisms, bacteria can potentially have global effects, Zakem says. For instance, as more bacteria switch over to anaerobic forms of respiration in deoxygenated zones, they may consume more nitrogen and give off as a byproduct nitrogen dioxide, which can be released back into the atmosphere as a potent greenhouse gas.</p>
<p>“We can think of this switch in bacteria as setting the ocean’s fertility,” Zakem says. “When nitrogen is lost from the ocean, you’re losing accessible nutrients back into the atmosphere. To know how much denitrification and nitrogen dioxide flux will change in the future, we absolutely need to know what controls that switch from using oxygen to using nitrogen. In that regard, this work is very fundamental.”</p>
<p>This research was supported, in part, by the Gordon and Betty Moore Foundation, the Simons Foundation, NASA, and the National Science Foundation.</p>
MIT oceanographers have found that some small marine organisms — mostly bacteria — have a surprisingly low limit to the amount of oxygen they need to breathe.Image: MIT NewsBacteria, EAPS, Environment, Evolution, Global Warming, Greenhouse gases, Oceanography and ocean engineering, Research, School of Science, Climate change, Microbes, ClimateJoern Callies and Jill McDermott win Carl-Gustaf Rossby Awards for PhD theseshttps://news.mit.edu/2016/callies-mcdermott-win-rossby-awards-1104
Awards to recent alumni honor the memory of Carl-Gustaf Rossby, a pioneer in earth and atmospheric sciences. Fri, 04 Nov 2016 13:30:01 -0400Lauren Hinkel | Oceans at MIThttps://news.mit.edu/2016/callies-mcdermott-win-rossby-awards-1104<p>Joern Callies PhD '16 and Jill McDermott PhD '15 were recently honored with the the&nbsp;<a href="http://paoc.mit.edu/paoc/education/rossby.htm" target="_blank">Carl-Gustaf Rossby Award</a>, given for the best PhD thesis completed within MIT's Program in Atmospheres, Oceans and Climate (PAOC).</p>
<p>As a major figure in the founding of the modern dynamical study of the atmosphere and ocean, Professor <a href="https://en.wikipedia.org/wiki/Carl-Gustaf_Rossby" target="_blank">Carl-Gustaf Rossby</a>’s name is recalled ubiquitously in the fields of Earth and planetary sciences. Rossby waves, the Rossby number, and the Rossby radius of deformation are ideas fundamental to the understanding of all fluid behaviors on a global scale. These insights into the large-scale air movement and mathematical descriptions of atmospheric and oceanic motion are among the reasons that Rossby is credited with the development of modern meteorology.</p>
<p>Further, it was at MIT that Rossby honed much of this work. After being appointed to the faculty in the Department of Aeronautics in 1928, Rossby&nbsp;founded the study of meteorology and physical oceanography at MIT, and later developed the first Department of Meteorology in an academic institution in the United States. While here, he made significant strides in the understanding of atmospheric heat exchange and turbulence, and relationships between ocean currents and the atmosphere.</p>
<p>In formulating their decision, the current Rossby Award Committee — comprised of professors Glenn Flierl, Mick Follows (chair), and Ron Prinn — solicited nominations from the thesis defense chairs of PAOC students graduating in academic years 2014-15 and 2015-16. In recognition of their work, McDermott and Callies will each receive a cash award and certificate.</p>
<p><strong>Understanding ocean turbulence</strong></p>
<p>In his doctoral dissertation, <a href="http://joernc.mit.edu/" target="_blank">Joern Callies</a>, now an MIT postdoc, reported <a href="https://mit.dspace.org/handle/1721.1/103253" target="_blank">his work</a> to understand the nature and dynamics of sub-mesoscale motions in the ocean — turbulence that occurs in the top 100 meters. Occurring on scales that are difficult to observe systematically, features at this scale are implicated in the transfer of material — particularly carbon — and heat between the atmosphere and surface waters and interior of the ocean. “We were trying to understand what energizes these sub-mesoscale flows, and there was a paradigm that they were driven by mesoscale frontogenesis,” Callies says. These consist of ocean eddies about 1,000 meters deep that pinch together at the surface and form temperature fronts. “But when I started looking at observations for evidence of this process, we didn’t really find the characteristics that were predicted.” Yet, to date, a clear theoretical and mechanistic understanding has been elusive.</p>
<p>Using theory, simulations, and elegant analysis of observed data, Callies identified regional variations in the nature of submesoscale features. “Instead we found that this turbulence is more energetic in winter than it is in summer, and that it’s more energetic in the surface layer that’s well-mixed in the winter, than it is below,” he explains. His findings suggested that there were different mechanisms at play during different seasons, and in his thesis, he highlighted the role of baroclinic instability and seasonal variations in the mixed-layer as key controls. These are instabilities that laterally slide warm water over cold, creating horizontal motion and can be characterized at the sub-mesoscale range. “That [movement] has implications for how the flow evolves and how it exchanges properties vertically. Then I followed that up, trying to understand turbulence driven by this mechanism.”</p>
<p>In a series of chapters, his thesis builds to provide a new and comprehensive view of these features. Professor Raffaele Ferrari&nbsp;advised Callies during the preparation of his thesis, and several chapters have been published and are already well cited.</p>
<p>Callies remains in the MIT Department of Earth, Atmospheric and Planetary Sciences as a postdoc. Next fall, he will take up a position as an assistant professor at Caltech. Callies’ current research aims at improving our understanding of the ocean circulation and its role in climate. With a continuing interest in the dynamics and impacts of sub-mesoscale turbulence in the upper ocean, Callies is focusing on fronts and currents 1-10 kilometers in horizontal extent, which are thought to achieve important exchanges of heat, carbon, and other tracers between the surface and interior ocean. He is also greatly interested in the large-scale circulation of the abyssal ocean, which connects the vast deep-ocean reservoirs of heat and carbon with the atmosphere and thus plays a crucial role in setting the pace of past and future climate change.</p>
<p><strong>Investigating hydrothermal vents </strong></p>
<p>In her doctoral dissertation,&nbsp;MIT-WHOI Joint Program alumna <a href="http://jillmcdermott.weebly.com/" target="_blank">Jill McDermott</a> shared <a href="https://dspace.mit.edu/handle/1721.1/97337" target="_blank">her work</a> to understand the geochemical nature of the sources of reduced carbon at diverse newly discovered hydrothermal vents.&nbsp;This is an important question since abiotically produced hydrogen and hydrocarbons provide energy for chemoautotrophic life in the deep sea with particular significance for understanding the origins of life on Earth.</p>
<p>To do this, McDermott joined a multidisciplinary team, hunting for hydrothermal vents along the Mid-Cayman Rise, an ultraslow spreading center and the deepest known mid-ocean ridge on Earth. After finding two vents, McDermott went to sea, measuring dissolved methane to trace the plume signals to their source, where she sampled vent fluids.</p>
<p>Over the next three years, McDermott performed a comprehensive array of chemical and isotopic analysis on inorganic and organic compound samples from multiple vents. She analyzed these with thermodynamic and mixing models to infer that the significant source of methane at the vents is derived from fluid inclusions in the host rocks, while other reduced carbon compounds are formed in the hydrogen rich vent fluids at the springs. In ocean floor fissures like these vents, “the fluids undergo reactions with rock at high temperatures and pressures, become buoyant and rise to the seafloor, where they play a role in modulating global seawater chemistry and supporting chemosynthetic ecosystems at the seafloor and in the chemical-rich plume.” She also measured multiple sulfur isotopes in metallic and hydrogen sulfides and sulfur, and used them to constrain sulfur sources and past hydrothermal activity. Her pioneering thesis work was published in two impactful first-authored papers.</p>
<p>“My thesis generated several new ideas under investigation, such as understanding the abundance and distribution of hydrocarbons in seafloor rocks, and experimentally testing hypotheses about H<sub>2</sub>&nbsp;generation and organic abiotic synthesis reactions at high temperatures and pressures,” she says.</p>
<p>McDermott is now an assistant professor in the Earth and Environmental Sciences Department at Lehigh University, where she continues to investigate the aqueous and volatile geochemistry and biogeochemistry of seafloor hydrothermal vents and ancient terrestrial fracture waters tapped by deep mines. These systems link fundamental geologic and biological processes that sustain microbial life in the largely unexplored deep subsurface biosphere, and they represent modern analogues of environments that may have played a critical role in the origin of life on the early Earth.</p>
<p>During her time with MIT and WHOI, McDermott received support and feedback from her advisors Jeffrey S. Seewald, and Christopher R. German (WHOI), who left a lasting impression on her and her work. “I am grateful for the scientific creativity and cheerful outlook of my advisors and committee members, who continually encourage my research and career endeavors,” McDermott says. “I found my thesis work to be simultaneously challenging, motivating and energizing, and I am grateful for the talented group of researchers, technical staff, administrators, and fellow students with whom I worked at MIT and WHOI.”</p>
Joern Callies (left) and Jill McDermottPhotos courtesy of Joern Callies and Jill McDermott.Awards, honors and fellowships, Alumni/ae, EAPS, Oceanography and ocean engineering, Program in Atmospheres, Oceans, and Climate, ResearchIra Dyer, professor emeritus of ocean engineering, dies at 91https://news.mit.edu/2016/ira-dyer-professor-emeritus-ocean-engineering-dies-1025
Former head of MIT&#039;s Department of Ocean Engineering is remembered for his innovation, entrepreneurship, and vision for ocean engineering.Tue, 25 Oct 2016 11:20:32 -0400Department of Mechanical Engineeringhttps://news.mit.edu/2016/ira-dyer-professor-emeritus-ocean-engineering-dies-1025<p>Ira Dyer, professor emeritus of ocean engineering, died peacefully at his home on Oct. 9 at the age of 91.</p>
<p>Dyer’s distinguished career, with a specialty in acoustics, spanned over six decades. His seminal research had profound impacts in the fields of aeroacoustics, structural acoustics, and underwater acoustics.</p>
<p>Dyer was a valued educator and mentor for many students who are now prominent scientists, and he served as head of MIT's Department of Ocean Engineering (which later merged with the Department of Mechanical Engineering) for 10 years. He also served as president of the Acoustical Society of America and on numerous committees, blue ribbon panels, and advisory boards for government agencies and research companies.</p>
<p>Born in Brooklyn, New York, in 1925, Dyer was the son of Frieda and Charles Dyer, who immigrated to the United States after being forced to flee the Pale of Settlement region of Russia. Dyer thrived as a student at Brooklyn Tech, where his scientific interests were nurtured. He served in the Army Air Corps during World War II, and studied at MIT under the GI bill following the war, receiving his PhD in physics in 1954. In 1949 Dyer married his sweetheart, Betty Schanberg of Clinton, Massachusetts. They were happily married for 68 years.</p>
<p>After his graduate studies, Dyer joined Bolt, Beranek, and Newman Inc., now BBN Technologies. He was hired by Leo Beranek, who would later say that Dyer was one of the three most important people responsible for the success of the company. In one of his first projects, Dyer designed, built, and tested an ultrasonic brain scanner. This system was intended to use active sonar to find brain tumors, and Dyer himself was the first person to undergo an ultrasonic brain scan. The system ended up only measuring bone thickness, but it paved the way for the ultrasonic scanners currently used in cardiology and gynecology.</p>
<p>Dyer later led others in an applied research division that investigated all aspects of sound and vibration in complex structures such as ships, submarines, aircraft, and spacecraft, which resulted in many publications in the <em>Journal of the Acoustical Society of America (JASA)</em>. During the mid 1950s, Dyer helped design the U.S. Navy X-1 submarine, a small four-person diesel-electric sub with a very quiet radiated noise mission. He designed an innovative "triple-stage isolation" engine-mounting system that significantly quieted the vehicle, allowing the submarine to pass sound restrictions. The isolation concept led the way for the U.S. Navy to develop ultraquiet submarines, which provided significant advantages for U.S. submarine operations during the Cold War.</p>
<p>In 1960, the Acoustical Society of America honored Dyer’s early work with its Biennial Award, a recognition to scientists under 35 for their outstanding contributions to acoustics.</p>
<p>In 1971, Dyer became head of the MIT Department of Ocean Engineering, which eventually merged with the Department of Mechanical Engineering in 2005. At its helm, he led the department into new areas of ocean engineering that emphasized learning about the ocean environment. Later, Dyer was named the Weber-Shaughness Professor of Ocean Engineering. His expertise and graduate course in ocean acoustics were legendary; he was a consummate professor, both as a lecturer and one-on-one, with a clarity that inspired his students.</p>
<p>In July of 1973, Dyer became director of the Sea Grant Program at MIT. Under his leadership, the Sea Grant Program, created to stimulate research and wise use of the oceans, became a model program, and was widely emulated. Dyer also nurtured other new subjects in ocean acoustics, especially in conjunction with the MIT-Woods Hole Oceanographic Institution Joint Program. For many years Dyer played a major role in advising, researching, and designing anti-submarine warfare systems for the Navy, keeping our nation safe during the Cold War.</p>
<p>Dyer made many seminal contributions to acoustics that were published in <em>JASA. </em>His article on the scintillation of ocean ambient noise is still one of the most cited today, as are his significant contributions to structural acoustics, reverberation, and propagation of sound in the sea. The programs Dyer established in these technical areas were international in scope.</p>
<p>Beginning in 1978, Dyer led and participated in six Arctic field programs. The first, the Canadian Basin Arctic Reverberation Experiment, imaged the entire Arctic basin with acoustics, providing evidence of seamounts. He and his students developed a taxonomy of ice noise events that has been fundamental for understanding Arctic noise. In the 1990s, Dyer resumed his research on structural acoustics that influenced contemporary submarine designs: He contributed to one high-level Navy technical advisory committee that led to the contemporary submarine sonar signal-processing suite.</p>
<p>Dyer was a fellow of the Acoustical Society of America and of the Institute of Electrical and Electronic Engineers; a member of the National Academy of Engineering; and a visiting fellow of Emmanuel College at Cambridge University. He was the recipient of many awards and honors in his long and distinguished career; in 1996 he was awarded the Per Bruel Gold Medal by the Acoustical Society of America, its highest honor.</p>
<p>After the collapse of the Soviet Union, Dyer and his wife, Betty, worked with the organization Action of Soviet Jewry to help place Soviet refugees in appropriate jobs, and they also sponsored a newly arrived family. Dyer was also a longtime philanthropist, with gifts benefiting medical research, the arts, community causes, MIT, and Clark University in Worcester, Massachusetts.</p>
<p>As an independent research consultant during the past 20 years, Dyer served on the board of directors and provided expertise to local ocean acoustic consulting firms founded by some of his former students. He was instrumental in helping to solve a pump vibration problem at the Deer Island Sewer Treatment facility; this problem impacted the construction completion schedule, and the solution allowed the project, a major construction project to eliminate Boston Harbor pollution, to move forward and the pump to operate safely.</p>
<p>Dyer’s joy was in challenging conventional thinking and being challenged by colleagues and students. If one of his students would say, “The data don’t agree with the theory,” Dyer would wag his finger and say, “No, no . . .&nbsp; The theory does not agree with the data!” Meetings with Dyer are still recalled with gusto. He challenged all to continuously learn and acquire knowledge. He took great pleasure in family and friends, and he will be deeply missed.</p>
<p>Dyer is survived by his wife, Betty; son Samuel Dyer and daughter-in-law Barbara; daughter Debora Dyer Mayer and son-in-law John; and three grandchildren: Ethan Dyer, Charley Mayer, and Owen Mayer.</p>
<p>Individuals wishing to make a donation in Dyer’s memory can do so to the following: Parents and Researchers Interested in Smith-Magenis Syndrome (<a href="http://www.PRISMS.org" target="_blank">PRISMS</a>), which supports those with a genetic disorder that Dyer’s oldest grandson was born with; <a href="http://www.caredimensions.org" target="_blank">Care Dimensions</a>, the North Shore hospice that was wonderful and loving to the Dyer family; or the <a href="https://giving.mit.edu/ira-dyer" target="_blank">Charles and Frieda Dyer Memorial Fund</a> (3413500), a tuition scholarship at MIT established by Ira and Betty in honor of Dyer's parents.</p>
MIT Professor Emeritus Ira DyerPhoto courtesy of the Dyer family.Faculty, Obituaries, Mechanical engineering, Oceanography and ocean engineering, School of EngineeringRaffaele Ferrari receives Cody Award in Ocean Scienceshttps://news.mit.edu/2016/raffaele-ferrari-receives-cody-award-ocean-sciences-1004
EAPS professor honored for excellence in oceanography.Tue, 04 Oct 2016 16:45:01 -0400Lauren Hinkel | Oceans at MIThttps://news.mit.edu/2016/raffaele-ferrari-receives-cody-award-ocean-sciences-1004<p>Raffaele Ferrari, the Cecil and Ida Green Professor in Earth and Planetary Sciences and Director of the MIT Program in Atmospheres, Oceans and Climate, has been selected to receive the 2016 Robert L. and Bettie P. Cody Award in Ocean Sciences.</p>
<p>The Scripps Institution of Oceanography at the University of California at San Diego biannually bestows <a href="https://scripps.ucsd.edu/people/awards/cody" target="_blank">the Cody Award</a> to a scientist in recognition of outstanding contributions to and achievement in physical oceanography, marine biology, and Earth science. While several individuals were considered for the prestigious prize, Ferrari’s “pioneering efforts toward understanding the nature and rates of oceanic mixing and their consequences for the general circulation,” were among several reasons for his selection.</p>
<p>MIT professor emeritus of physical cceanography <a href="https://eapsweb.mit.edu/people/wunsch" target="_blank">Carl Wunsch</a>’s seasoned insight and justification helped to settle the matter. The prize citation reads:</p>
<p>"Raffaele Ferrari is awarded the 2016 Cody Prize for his stimulating and collaborative work directed at mechanisms of oceanic mixing and their interesting and sometimes unexpected consequences. With colleagues he has worked to greatly improve the rendering of mixing processes in numerical models directed at climate change and along the way has illuminated mixing processes with special attention to the submesoscale near the ocean surface, the mixed-layer generally, and the internal tide/internal wave field in its interactions with topography. He has applied these ideas towards illuminating the oceanic energy field, the paleocirculation, and studied the consequences for climate change generally."</p>
<p><a href="http://ferrari.mit.edu/" target="_blank">Ferrari’s research</a> examines the circulation of the ocean, its impact on present and past climates, and its role on shaping biological productivity. His group combines observations, theory, and numerical models to investigate the physics and biology of the ocean from scales of centimeters to thousand of kilometers. He collaborates with several groups and centers across the institute, including the Climate Modeling Initiative, the MIT-Woods Hole Oceanographic Institution Joint Program and MIT General Circulation Model.</p>
<p>In addition to the accolade, Scripps Institution of Oceanography has invited Ferrari to present the Cody Award public lecture at 3 p.m. on Oct. 12 in the Robert Paine Scripps Forum for Science, Society and the Environment (Scripps Seaside Forum), in La Jolla, California, as well as another talk at UC San Diego on his work later this year. Ferrari’s lecture, “The Role of Ocean Turbulence in Climate,” will show how small-scale ocean features can translate significant effects to the larger ocean and climate systems, but because of their size, they are too small to be incorporated into global climate models. Atmospheric clouds share a similar issue.</p>
<p>“Clouds are the Achilles heel of our atmosphere models,” said <a href="https://scripps.ucsd.edu/news/public-lecture-dives-ocean-turbulence-and-climate" target="_blank">Ferrari in a statement</a>. “In the lecture we will explore the Achilles heels of ocean models, how they impact our understanding of present and past climates, and the progress we are making in healing the heels.”</p>
<p>In the moments between his research pursuits, Ferrari directs the Program in Atmospheres, Oceans and Climate (PAOC), coordinates outreach events and stories with Oceans at MIT — an organization that pulls together all oceans-related content from MIT and WHOI — and is helping to oversee and direct the upcoming Climate@MIT group.</p>
<p>Before arriving at MIT, Ferrari attended the Scripps Institution of Oceanography and Polytechnic University of Turin, earning PhDs in physical oceanography and fluid dynamics, respectively. So, when Ferrari learned that he’d be the 13th recipient of the Cody Award, the selection held a special significance.</p>
<p>“I was a graduate student at Scripps from 1995 until 2000, so I am particularly honored to receive an award from my alma mater,” Ferrari said. “I remember attending the Cody Award lectures as a student, but I never imagined I would be delivering one in the future.”</p>
<p>The endowment for the Cody Award was established by the late Robert Cody and his wife Bettie, along with a significant contribution from Capital Research and Management Company, in recognition of Robert Cody's service to the Los Angeles-based firm.</p>
MIT Professor Raffaele Ferrari has been selected to receive the 2016 Robert L. and Bettie P. Cody Award in Ocean Sciences.Photo courtesy of Raffaele Ferrari.Awards, honors and fellowships, Faculty, EAPS, Ocean science, Oceanography and ocean engineering, Climate, Climate change, Oceans at MIT, School of ScienceResearchers find explanation for interacting giant, hidden ocean waveshttps://news.mit.edu/2016/researchers-find-explanation-for-interacting-giant-hidden-ocean-waves-0928
Better simulations of internal tides may benefit sonar communications, protect offshore structures, and more.Wed, 28 Sep 2016 00:00:00 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2016/researchers-find-explanation-for-interacting-giant-hidden-ocean-waves-0928<p>In certain parts of the ocean, towering, slow-motion rollercoasters called internal tides trundle along for miles, rising and falling for hundreds of feet in the ocean’s interior while making barely a ripple at the surface. These giant, hidden swells are responsible for alternately drawing warm surface waters down to the deep ocean and pulling marine nutrients up from the abyss.</p>
<p>Internal tides are generated in part by differences in water density, and created along continental shelf breaks, where a shallow seafloor suddenly drops off like a cliff, creating a setting where lighter water meets denser seas. In such regions, tides on the surface produce oscillating, vertical currents, which in turn generate waves below the surface, at the interface between warmer, shallow water, and colder, deeper water. These subsurface waves are called “internal tides,” as they are “internal” to the ocean and travel at the same frequency as surface tides. Internal tides are largely calm in some regions but can become chaotic near shelf breaks, where scientists have been unable to predict their paths.</p>
<p>Now for the first time, ocean engineers and scientists from MIT, the University of Minnesota at Duluth (UMD), and the Woods&nbsp;Hole&nbsp;Oceanographic&nbsp;Institution (WHOI) have accurately simulated the motion of internal tides along a shelf break called the Middle Atlantic Bight — a region off the coast of the eastern U.S. that stretches from Cape Cod in Massachusetts to Cape Hatteras in North Carolina. They found that the tides’ chaotic patterns there could be explained by two oceanic “structures”: the ocean front at the shelf break itself, and the Gulf Stream — a powerful Atlantic current that flows some 250 miles south of the shelf break.&nbsp;&nbsp;</p>
<p>From the simulations, the team observed that both the shelf break and the Gulf Stream can act as massive oceanic walls, between which internal tides ricochet at angles and speeds that the scientists can now predict.</p>
<p>The researchers have published their findings in the <em>Journal of Geophysical Research: Oceans </em>and the <em>Journal of Physical Oceanography. </em>The team includes Samuel Kelly, an assistant professor at UMD who was a postdoc at MIT for this research; Pierre Lermusiaux, an associate professor of mechanical engineering and ocean science and engineering at MIT; Tim Duda, a senior scientist at WHOI; and Patrick Haley, a research scientist at MIT.</p>
<p>Lermusiaux says the team’s simulations of internal tides could help to improve sonar communications and predict ecosystems and fishery populations, as well as protect offshore oil rigs and provide a better understanding of the ocean’s role in a changing climate.</p>
<p>“Internal tides are a big chunk of energy that’s input to the ocean’s interior from the common [surface] tides,” he explains. “If you know how that energy is dissipated and where it goes, you can provide better predictions and better understand the ocean and climate in general.”</p>
<p><strong>“Dead calm”</strong></p>
<p>The effects of internal waves were first reported in the late 1800s, when Norwegian sailors, attempting to navigate a fjord, experienced a strange phenomenon: Even though the water’s surface appeared calm, their ship seemed to strongly resist sailing forward — a phenomenon later dubbed “dead water.”</p>
<p>“It would be dead calm in the water, and you’d turn your ship on but it wouldn’t move,” Lermusiaux says. “Why? Because the ship is generating internal waves because of the density difference between the light water on top and the salty water on the bottom in the fjord, that keep you in place.”</p>
<p>Since then, scientists have found that surface tides, just like internal tides, are generated by the cyclical, gravitational pull of the sun and the moon, and travel between density-varying mediums. Surface waves travel at the boundary between the ocean and the air, while internal waves and internal tides flow between water layers of varying density.</p>
<p>“What people didn’t really know was, why can those internal tides be so variable and intermittent?” Duda says.</p>
<p><strong>Following the tide</strong></p>
<p>In the summer of 2006, oceanographers embarked on a large-scale scientific cruise, named “<a href="http://www.whoi.edu/oceanus/viewArticle.do?id=29087&amp;sectionid=1000">Shallow Water ’06</a>,” to generate a detailed picture of how sound waves travel through complex coastal waters, specifically along part of the Middle Atlantic Bight region. The experiment confirmed that internal tides stemmed from the region’s shelf break at predictable intervals. Puzzlingly, the experiment also showed that internal tides arrived back at the shelf break at unpredictable times and locations.</p>
<p>“One would think if they were all generated at the shelf break, they would be more or less uniform, in and out,” Lermusiaux says.</p>
<p>To solve this puzzle, Lermusiaux, Haley, and their colleagues incorporated data from the 2006 cruise into hydrodynamic simulations to represent tides in a realistic ocean environment. These data-driven simulations included not only tides but also “background structures,” such as density gradients, eddies, and currents such as the Gulf Stream, with which tides might interact.</p>
<p>After completing more than 2,500 simulations of the Middle Atlantic Bight region, they observed that internal tides generated close to the shelf break seemed to flow out toward the ocean, only to bounce back once they reached the Gulf Stream. As the Gulf Stream meandered, the exact direction and location of the internal tides became more variable.</p>
<p>"Looking at the initial plots from the simulations, it was obvious that some type of interaction was happening between the internal tide and Gulf Stream,” Kelly says. “But the simulations could produce a huge number of complicated interactions and there are lots of theories for different types of interactions. So we started testing different theories.”</p>
<p><strong>Terms of agreement</strong></p>
<p>The researchers sought to find mathematical equations that would describe the underlying fluid dynamics that they observed in their simulations. To do this, they started with an existing equation that characterizes the behavior of internal tides but involves an idealized scenario, with limited interactions with other features. The team added new “interaction terms,” or factors, into the equations that described the dynamics of the Gulf Stream and the shelf break front, which they derived from their data-driven simulations.</p>
<p>“It was really exciting when we wrote down a set of slightly idealized equations and saw that the internal tides extracted from the complex simulations were obeying almost the exact same equations," Kelly says.</p>
<p>The match between their simulations and equations indicated to the researchers that the Gulf Stream and the shelf break front were indeed influencing the behavior of the internal tides. With this knowledge, they were able to accurately predict the speed and arrival times of internal waves at the shelf break, by first predicting the strength and position of the Gulf Stream over time. They also showed that the strength of the shelf break front alters the speed and arrival times of internal tides.</p>
<p>The team is currently applying their simulations to oceanic regions around Martha’s Vineyard, the Pacific Islands, and Australia, where internal tides are highly variable and their behavior can have a large role in shaping marine ecosystems and mediating the effects of climate change.</p>
<p>“Our work shows that, with data-driven simulations, you can find and add missing terms, and really explain the ocean’s interactions,” Lermusiaux says. “If you look at ocean or atmospheric sciences today, understanding interactions of features is where big questions are.”</p>
<p>This research was funded in part by the Office of Naval Research and the National Science Foundation.</p>
Ocean engineers from MIT, the University of Minnesota at Duluth, and the Woods Hole Oceanographic Institution have accurately simulated the motion of internal tides along a shelf break called the Middle Atlantic Bight — a region off the coast of the eastern U.S. that stretches from Cape Cod in Massachusetts to Cape Hatteras in North Carolina.Image: Google EarthFluid dynamics, Oceanography and ocean engineering, Mechanical engineering, Ocean science, Research, Water, School of Engineering, Environment, Woods Hole, National Science Foundation (NSF)Computing the ocean’s true colorshttps://news.mit.edu/2016/computing-oceans-true-colors-stephanie-dutkiewicz-0915
Stephanie Dutkiewicz’ phytoplankton models project the future of the ocean as food source and carbon sink.Thu, 15 Sep 2016 16:45:01 -0400Mark Dwortzan | MIT Joint Program on the Science and Policy of Global Changehttps://news.mit.edu/2016/computing-oceans-true-colors-stephanie-dutkiewicz-0915<p>When she was 17, <a href="http://globalchange.mit.edu/about/our-people/personnel/all_id/46" target="_blank">Stephanie Dutkiewicz</a> set sail from her native South Africa to the Caribbean islands. Throughout a three-month journey, she noticed that the color of the ocean shifted from place to place, but it wasn’t until she took up oceanography in college that she came to understand why. Early on in her studies, she learned that ocean color varies from green to blue, depending on the type and concentration of phytoplankton (algae) in the area. As they use chlorophyll, a green pigment, to generate organic carbon through photosynthesis, these “plants of the sea” reflect light; the more phytoplankton in the ocean, the less blue and more green the color of the water.</p>
<p>Now a principal research scientist in MIT’s Joint Program on the Science and Policy of Global Change&nbsp;and Department of Earth, Atmospheric and Planetary Sciences (EAPS), Dutkiewicz remains focused on these drivers of ocean color. For more than a decade, she and her main research partner, EAPS Associate Professor <a href="http://globalchange.mit.edu/about/our-people/personnel/all_id/60" target="_blank">Mick Follows</a>, have been leading a team of a dozen MIT researchers and several collaborators from universities around the world to advance the <a href="http://darwinproject.mit.edu/" target="_blank">Darwin Project</a>, which aims to model the growth, loss, and movement of phytoplankton around the world, the environments that they inhabit, and how they affect one another.</p>
<p>Dutkiewicz is systematically probing phytoplankton behavior to home in on what traits distinguish one of thousands of phytoplankton species from another, which types will survive and thrive under different environmental conditions, and where different types are likely to live. Guided by laboratory, ship, and satellite observations, she has represented as many as 100 different types of phytoplankton — other groups typically model no more than five — in complex computer models that simulate phytoplankton population dynamics in the ocean and project how those dynamics will change in coming decades.</p>
<p>Producing results that square with actual observations, these models, which comprise hundreds of thousands of lines of code, are generating the world’s most complex 2-D and 3-D global maps of phytoplankton activity and ocean color. Visually arresting, the maps suggest profound implications for the future of the planet, from the sustainability of the ocean’s food web to the pace of global warming.</p>
<p>“Since they are at the base of the food web, understanding which types of phytoplankton live where and projecting how these populations are likely to change will help us understand what will happen further up the food chain,” Dutkiewicz explains. “And because the process by which these phytoplankton take carbon and sink it down into the deep ocean is responsible for storing about 200 parts per million (ppm) of carbon dioxide, they play an important role in the Earth’s climate system.”</p>
<p><strong>Size matters </strong></p>
<p>In an ongoing phytoplankton modeling study funded by the National Science Foundation, Dutkiewicz and Follows are investigating several distinguishing traits and their potential impact on the planet. Traits they’ve identified include those based on behavior, such as rates of nutrient uptake, temperature tolerance and light tolerance, and those based on size.</p>
<p>In the phytoplankton world, size matters. While all are microscopic, individual phytoplankton range in diameter from under 1 micrometer to more than 1,000 micrometers — akin to the size difference between a mouse and Manhattan. As the ocean warms, its upper layers are expected to interact less with lower layers where nutrients are concentrated. As a result, smaller phytoplankton, which are best equipped to tolerate compromised nutrient conditions, will likely outnumber larger phytoplankton, which are more effective at storing carbon. Such changes may not only shift the oceanic food web to one based on smaller phytoplankton but also reduce the ocean’s effectiveness as a carbon sink.</p>
<p>Most phytoplankton models, including those used by the Intergovernmental Panel on Climate Change (<a href="http://www.ipcc.ch/" target="_blank">IPCC</a>), usually resolve just two phytoplankton types: small and large. So when the ocean warms to a certain point in the coming decades, the modelled phytoplankton populations appear to shift dramatically, with small ones far outnumbering large ones. In reality, however, these shifts are expected to occur gradually.</p>
<p>“Because we include a more diverse size distribution in our model, we find that as we run out the 21st century, phytoplankton sizes don’t quickly shift from big to small, but rather from big to slightly smaller,” says Dutkiewicz. “So the impact might not be as large as the IPCC models predict.”</p>
<p>To assess the impact of phytoplankton size and function on the climate, Dutkiewicz and her collaborators represent the global ocean as a set of location-based grid cells, each sized at a resolution that’s fine enough to validate the model through satellite and ship observations. Within each grid cell, the model solves a set of equations that account for phytoplankton growth, movement, loss, carbon cycling and other population dynamics.</p>
<p><strong>True colors </strong></p>
<p>With funding from NASA, Dutkiewicz is also using the computer model to "ground-truth" satellite observations of phytoplankton concentrations in different parts of the ocean, which are based on how much light is emitted from the ocean surface. The light is reflected by chlorophyll in phytoplankton, which absorb more blue than green light. By measuring how much blue versus green light is emitted, the satellites estimate how much chlorophyll is present at a given location. Such estimates are crude at best, so Dutkiewicz is working to assess the level of uncertainty in chlorophyll ocean maps by representing reflected light in her phytoplankton models.</p>
<p>Her models produce true colors of the ocean today, and project ocean colors throughout the 21st century based on changes in phytoplankton population dynamics. For example, as the ocean warms and becomes more acidic, phytoplankton populations will change, thus altering chlorophyll levels and impacting how much light is reflected from the ocean surface.</p>
<p>“Tracking this could help us identify a real, climate-change-driven signal that stands out from the year-to-year, natural variability in phytoplankton populations across the globe,” she says.</p>
<p>Dutkiewicz’ career path as an oceanographer has uniquely positioned her to pinpoint such signals. As a PhD student in physical oceanography at the University of Rhode Island, she originally focused on capturing the movement of ocean currents. When she came to MIT in 1998 as a postdoc in EAPS, she studied how physics alters the biology of phytoplankton (e.g. how ocean currents move their biological cargo), and built a numerical model of the marine ecosystem based on one type of phytoplankton. Now modeling up to 100 times as many types, she is perhaps the most qualified person in the world to explain not only why the colors of the ocean vary from place to place, but also what those colors might portend for the future of the planet.</p>
<p><em>This article originally appeared in the Summer 2016 issue of </em><a href="http://globalchange.mit.edu/files/sponsors-only/GlobalChanges-Summer2016.pdf" target="_blank">Global Changes</a>,<em> a triennial publication of the MIT Joint Program on the Science and Policy of Global Change.&nbsp;</em></p>
MIT research scientist Stephanie Dutkiewicz in her office with a display of her phytoplankton model simulation Photo: MIT Joint Program on the Science and Policy of Global ChangeResearch, Profile, Carbon, Climate, Climate change, Earth and atmospheric sciences, Environment, Phytoplankton, Oceanography and ocean engineering, School of Science, National Science Foundation (NSF), Center for Global Change Science, Joint Program on the Science and Policy of Global Change, EAPSStudy finds increased ocean acidification due to human activitieshttps://news.mit.edu/2016/increased-ocean-acidification-human-activities-0907
More anthropogenic carbon in the northeast Pacific means weaker shells for many marine species.Wed, 07 Sep 2016 00:00:00 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2016/increased-ocean-acidification-human-activities-0907<p>Oceanographers from MIT and Woods Hole Oceanographic Institution report that the northeast Pacific Ocean has absorbed an increasing amount of anthropogenic carbon dioxide over the last decade, at a rate that mirrors the increase of carbon dioxide emissions pumped into the atmosphere.</p>
<p>The scientists, led by graduate student Sophie Chu, in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, found that most of the anthropogenic carbon (carbon arising from human activity) in the northeast Pacific has lingered in the upper layers, changing the chemistry of the ocean as a result. In the past 10 years, the region’s average pH has dropped by 0.002 pH units per year, leading to more acidic waters. The increased uptake in carbon dioxide has also decreased the availability of aragonite — an essential mineral for many marine species’ shells.</p>
<p>Overall, the researchers found that the northeast Pacific has a similar capacity to store carbon, compared to the rest of the Pacific. However, this carbon capacity is significantly lower than at similar latitudes in the Atlantic.</p>
<p>“The ocean has been the only true sink for anthropogenic emissions since the industrial revolution,” Chu says. “Right now, it stores about 1/4 to 1/3 of the anthropogenic emissions from the atmosphere. We’re expecting at some point the storage will slow down. When it does, more carbon dioxide will stay in the atmosphere, which means more warming. So it’s really important that we continue to monitor this.”</p>
<p>Chu and her colleagues have published their results in the <em>Journal of Geophysical Research: Oceans.</em></p>
<p><strong>Tipping the scales</strong></p>
<p>The northeast Pacific, consisting of waters that flow from Alaska’s Aleutian Islands to the tip of southern California, is considered somewhat of a climate canary — sensitive to changes in ocean chemistry, and carbon dioxide in particular. The region sits at the end of the world’s ocean circulation system, where it has collected some of the oldest waters on Earth and accumulated with them a large amount of dissolved inorganic carbon, which is naturally occurring carbon that has been respired by marine organisms over thousands of years.</p>
<p>“This puts the Pacific at this already heightened state of high carbon and low pH,” Chu says.</p>
<p>Add enough atmospheric carbon dioxide into the mix, and the scales could tip toward an increasingly acidic ocean, which could have an effect first in sea snails called pteropods, which depend on aragonite (a form of calcium carbonate) to make their protective shells. More acidic waters can make carbonate less available to pteropods.</p>
<p>“These species are really sensitive to ocean acidification,” Chu says. “It’s harder for them to get enough carbonate to build their shells, and they end up with weaker shells, and have reduced growth rates.”</p>
<p><strong>Protecting shells</strong></p>
<p>Chu and her colleagues originally set out to study the effects of ocean acidification on pteropods, rather than the ocean’s capacity to store carbon. In 2012, the team embarked on a scientific cruise to the northeast Pacific, where they followed the same route as a similar cruise in 2001. During the month-long journey, the scientists collected samples of pteropods, as well as seawater, which they measured for temperature, salinity, and pH.</p>
<p>Upon their return, Chu realized that the data they collected could also be used to gauge changes in the ocean’s anthropogenic carbon storage. Ordinarily, it’s extremely difficult to tease out anthropogenic carbon in the ocean from carbon that naturally arises from breathing marine organisms. Both types of carbon are classified as dissolved inorganic carbon, and anthropogenic carbon in the ocean is miniscule compared to the vast amount of carbon that has accumulated naturally over millions of years.</p>
<p>To isolate anthropogenic carbon in the ocean and observe how it has changed through time, Chu used a modeling technique known as extended multiple linear regression — a statistical method that models the relationships between given variables, based on observed data. The data she collected came from both the 2012 cruise and the previous 2001 cruise in the same region.</p>
<p>She ran a model for each year, plugging in water temperature, salinity, apparent oxygen utilization, and silicate. The models then estimated the natural variability in dissolved inorganic carbon for each year. That is, the models calculated the amount of carbon that should vary from 2001 to 2012, only based on natural processes such as organic respiration. Chu then subtracted the 2001 estimate from the 2012 estimate — a difference that accounts for sources of carbon that are not naturally occurring, and are instead anthropogenic.</p>
<p><strong>Sinking carbon</strong></p>
<p>The researchers found that since 2001, the northeast Pacific has stored 11 micromoles per kilogram of anthropogenic carbon, which is comparable to the rate at which carbon dioxide has been emitted into the atmosphere. Most of this carbon is stored in surface waters. In the northern part of the region in particular, anthropogenic carbon tends to linger in shallower waters, within the upper 300 meters of the ocean. The southern region of the northeast Pacific stores carbon a bit deeper, within the top 600 meters.</p>
<p>Chu says this shallow storage is likely due to a subpolar gyre, or rotating current, that pushes water up from the deep, preventing surface waters from sinking. In contrast, others have observed that similar latitudes in the Atlantic have stored carbon much deeper, due to evaporation and mixing, leading to increased salinity and density, which causes carbon to sink.</p>
<p>The team calculated that the increase in anthropogenic carbon in the upper ocean caused a decrease in the region’s average pH, making the ocean more acidic as a result. This acidification also had an effect on the region’s aragonite, decreasing its saturation state over the last decade.&nbsp;&nbsp;</p>
<p>Richard Feely, a senior scientist at the National Oceanic and Atmospheric Administration, says that the group’s results show that this particular part of the ocean is “highly sensitive to ocean acidification.”</p>
<p>“Our own work with pteropods, and that of others, indicate that some marine organisms are already being impacted by ocean acidification processes in this region,” says Feely, who did not contribute to the study.&nbsp;“Laboratory studies indicate that many species of corals, shellfish, and some fish species will be impacted in the near future.&nbsp;As this study, and others, have shown, the region will soon become undersaturated with respect to aragonite later this century.”</p>
<p>While the total amount of anthropogenic carbon appears to be increasing with each year, Chu says the rate at which the northeast Pacific has been storing carbon has remained relatively the same since 2001. That means that the region could still have a good amount of “room” to store carbon, at least for the foreseeable future. But already, her team and others are seeing in the acidification trends the ocean’s negative response to the current rate of carbon storage.</p>
<p>“It would take hundreds of thousands of years for the ocean to absorb the majority of CO<sub>2</sub> that humans have released into the atmosphere,” Chu says. “But at the rate we’re going, it’s just way faster than anything can keep up with.”</p>
<p>This research was supported in part by the National Science Foundation Ocean Acidification Program, the National Institute of Standards and Technology, and the National Science Foundation Graduate Research Fellowship Program.</p>
“The ocean has been the only true sink for anthropogenic emissions since the industrial revolution,” says MIT graduate student Sophie Chu, pictured here. “Right now, it stores about 1/4 to 1/3 of the anthropogenic emissions from the atmosphere. We’re expecting at some point the storage will slow down.”
Photo: Zhaohui Aleck Wang/Woods Hole Oceanographic InstitutionClimate, Climate change, EAPS, Earth and atmospheric sciences, Emissions, Environment, Global Warming, Greenhouse gases, Oceanography and ocean engineering, Research, School of ScienceMicroscale marine interactions may shape critical carbon cycleshttps://news.mit.edu/2016/marine-microscale-interactions-may-shape-carbon-cycles-0630
New research finds interactions between microorganisms and marine particles may have significant effects on oceanic carbon cycling.Thu, 30 Jun 2016 15:50:01 -0400Department of Civil and Environmental Engineeringhttps://news.mit.edu/2016/marine-microscale-interactions-may-shape-carbon-cycles-0630<p>In 1930, the deep-sea explorer William Beebe became the first to observe “marine snow,” an ever-present undersea shower of flocculent organic particles composed of dead phytoplankton, zooplankton fecal pellets, and other nutrient-rich detritus. Globally, marine organic particles transport billions of tons of carbon each year from the surface to the deep ocean. The “valves” controlling this carbon flux are none other than microscopic collectives of marine microorganisms, which assemble on and collectively degrade sinking organic particles. However, how marine microorganisms self-assemble into communities on particles, and how these dynamics shape particle degradation, remains unclear.</p>
<p><strong>Microscale microbial community successions</strong></p>
<p>A new <a href="http://www.nature.com/ncomms/2016/160617/ncomms11965/full/ncomms11965.html" target="_blank">study</a>, published recently in <em>Nature Communications</em> and led by MIT graduate student Manoshi S. Datta and MIT Department of Civil and Environmental Engineering (CEE) Professor Otto X. Cordero, in collaboration with professors Martin Polz from CEE and Jeff Gore from the MIT Department of Physics, sheds new light on this area.</p>
<p>Traditionally, it has been difficult to characterize community assembly processes and their drivers on wild marine particles, since these particles can vary widely in age, size, and chemical composition. Therefore, the team used an alternative, “semi-wild” approach, in which they immersed synthetic, chemically defined particles in natural coastal seawater. This approach allowed the team to track the process of community assembly on particles with unprecedented spatiotemporal resolution.</p>
<p>The research shows that microorganisms in the ocean self-assemble into communities on particles through rapid sequential turnover: Certain bacterial taxa attach to and colonize particles, but leave in a matter of hours, only to be replaced by new bacterial taxa. This colonization sequence was surprisingly reproducible and followed a characteristic ecological pattern known as a “primary succession.” At early stages of succession, “pioneers” — bacterial taxa that were adapted to seek out and degrade organic particles — dominated particle-associated communities. However, pioneers paved the way for “secondary consumers,” bacterial taxa that were unable to degrade particles, but could exploit metabolic byproducts from pioneers in order to grow. Interestingly, such primary successions have long been observed in temperate forests. This new study shows that similar ecological dynamics occur within marine microbial communities, but on much shorter temporal (hours) and spatial (microns) scales.</p>
<p><strong>From microscopic dynamics to macroscopic consequences </strong></p>
<p>“Our results suggest that the existing theory of successions that has been developed for plants and animals may be applicable to complex natural microbial communities,” says Cordero, the lead senior author on this work. “This could provide a basis for linking microbial community structure to their population dynamics and activity.”</p>
<p>Furthermore, the research suggests that, through ecological successions, microbial communities on marine particles undergo a major transition, shifting from a collective metabolism dictated by particle nutrients to one determined by the metabolic byproducts of the pioneers. As a result, it is possible that particle-associated communities in the ocean are largely composed of bacteria that cannot degrade the particle, but instead rely on interactions with pioneers in order to survive. “We think these interactions between microbes — where the majority exploits the effort of the pioneer minority — may end up having major effects on carbon turnover in the ocean,” says Cordero, adding that such interactions could shift the balance between organic matter degradation and biomass build-up by microbes in the ocean.</p>
<p>“Microbial ecologists have long asked how microbial communities develop and change over time and if these community dynamics have implications for the way that ecosystems ultimately function,” says Scott Ferrenberg of the United States GS Canyonlands Research Station, who was not involved in the research. “These questions remain at the frontier of microbial ecology. This study is noteworthy for its approach to understanding community development over time and for teasing apart the feeding strategies in these diminutive, yet highly important marine microbes.”</p>
<p>“Our ability to measure microbial communities is just now reaching the point where we can begin to understand interactions among microbes in complex natural environments and the consequences of those interactions at ecosystem scales,” says Senior Research Scientist Stephen Lindemann at the Pacific Northwest National Laboratory, who also did not take part in the study. “This data importantly suggests that close interactions with particle-degrading microbes sustains a high diversity of secondary consumers in marine particle-associated communities. Ultimately, all microbial politics is local, too, and the sheer amount of marine snow means local microbial interactions within these communities may drive carbon cycling at whole-ocean scales.”</p>
Fluorescence microscopy reveals the surface of a single synthetic particle colonized by wild marine microorganisms (green), which are fluorescently labeled with a double-stranded DNA stain.Image courtesy of the researchers.Research, Microbes, Oceanography and ocean engineering, Ecology, Civil and environmental engineering, Physics, School of Engineering, School of ScienceSouthern Ocean cooling in a warming worldhttps://news.mit.edu/2016/southern-ocean-cooling-in-a-warming-world-0624
Research suggests Antarctica and the Southern Ocean may be experiencing a period of cooling before warming takes over, thanks to the ozone hole. Fri, 24 Jun 2016 17:35:02 -0400Lauren Hinkel | Oceans at MIThttps://news.mit.edu/2016/southern-ocean-cooling-in-a-warming-world-0624<p>Around the world, scientists are observing evidence of climate change — record high temperatures, rising sea levels, and melting ice sheets. But <a href="http://oceans.mit.edu/JohnMarshall/wp-content/uploads/2016/01/Kostov2016_TwoTimescales.pdf" target="_blank">new research</a> from MIT’s <a href="https://paocweb.mit.edu/" target="_blank">Program in Atmospheres, Oceans and Climate</a> indicates that Antarctica and the Southern Ocean may be experiencing a period of cooling before warming takes over — and the culprit might be the ozone hole rather than greenhouse gases.</p>
<p>“Our study tries to address one of the most mysterious problems of recent historical climate change in the region because, in contrast to the strong global warming trend, we’ve seen persistent cooling in the Southern Ocean and sea ice expansion,” says <a href="https://paocweb.mit.edu/people/yavor-kostov" target="_blank">Yavor Kostov</a> PhD '16, a recent MIT graduate and lead author on the study <a href="http://link.springer.com/article/10.1007%2Fs00382-016-3162-z">published in the journal <em>Climate Dynamics</em></a>. “And our study addresses some mechanisms that could be related to this persistent cooling trend.”</p>
<p>Kostov, along with oceanographer <a href="http://oceans.mit.edu/JohnMarshall/" target="_blank">John Marshall</a>, the Cecil and Ida Green Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS) and colleagues, used results from computer simulations with models called coupled general circulation models (CGM) and observations to better understand how the ocean, atmosphere, and ice interact together, which could lead sea surface temperatures to fall and sea-ice to expand round Antarctica.</p>
<p>He attributes this to a combination of circumstances unique to the Southern Ocean encircling Antarctica: “The Southern Ocean is a very special place,” Kostov says. Without a continental barrier in the way, the winds and water can flow relatively unobstructed in a generally eastward direction around Antarctica. And unlike other parts of the world’s oceans, salinity — not temperature — governs the stratification of the Southern Ocean, so layers of cold relatively fresh water float atop warmer saltier water. Moreover, the Antarctic is a region with significant ozone depletion, primarily due to chlorofluorocarbon (CFC) emissions. Ozone depletion in the stratosphere far above the Earth’s surface can “modify the pattern of atmospheric circulation all the way down to the ocean’s surface, and this change in the westerly winds then alters the way the ocean circulates. And we study exactly the effect of this change in the [Southern] Ocean circulation,” Kostov says.</p>
<p>Kostov and Marshall argue that sea surface temperatures and sea-ice around Antarctica initially cool and expand, respectively, in response to ozone-related changes in surface wind trends. This is because the strengthening of the westerly winds drives cold water equator-ward away from the Antarctica, encouraging sea-ice growth. However, on longer timescales, warm water is drawn up from below resulting in warming of sea surface temperatures and sea-ice decline. However, not all models transition from a period of surface water cooling and sea-ice expansion to warming and sea-ice loss.</p>
<p>What, then, is the mechanism that sets the crossover timescale from cooling to warming?</p>
<p>“Our paper suggests that the first process — the northward transport of colder water — dominates this fast cooling response, but then over longer time scales, we have this build-up of heat below the surface that impacts the slow timescale of response — the gradual warming,” Kostov says. As the winds force cold freshwater away from the Antarctic pole, warm saltwater underneath rises to replace it. “This is a slower mechanism because this temperature inversion — cold overlying warm water — is below this well-mixed surface there of the ocean, which changes its depth seasonally,” he continued. Each winter this mixed layer reaches deeper and takes up some of the heat which builds up because of anomalous upwelling. Eddies deep within the ocean may also interfere with the upwelling of warm water, contributing to the slow warming response seen in some of the models.</p>
<p>The takeaway is that we’ve identified a fundamental mechanism that allows the Southern Ocean to respond to the change in westerly winds, with initial cooling, but then we show that this might be followed by gradual warming. And we relate this fundamental response to its climatological temperature gradients. So one message is: It’s important that models have the right Southern Ocean climatology to be able to get this response to this shift in the winds.</p>
<p>In a world that is increasingly feeling the effects of global warming, Kostov remarks that this new research can help improve climate science and inform policy. Understanding the climate mechanisms at play in the Southern Ocean can not only explain observances of cooling there, but also why the Southern Ocean is able to absorb heat from the atmosphere and how it transports this heat northward where it can be stored deeper in the ocean. This is particularly important since over 90 percent of the world’s heat from human influences is stored in the World Ocean with a major contribution from the Southern Ocean, and this in turn affects the pace of global warming. Additionally, cooling around Antarctica is often contrasted against global warming, but studies like MIT’s help to explain that Southern Ocean cooling is one part of a larger evolving picture in the Earth’s climatological record. Kostov says that their study provides yet another scientific stepping-stone towards understanding the fundamentals surrounding Antarctic climate and ocean behaviors.</p>
<p>This project was supported by the <a href="http://map.nasa.gov/">NASA Map</a> program and the <a href="http://www.nsf.gov/geo/fesd/">National Science Foundation FESD</a> program.</p>
Observed sea surface temperature (SST) trends for 1982-2012 in degrees Celsius per decade. Image: Courtesy of the researchers.Oceans at MIT, Program in Atmospheres, Oceans, and Climate, Oceanography and ocean engineering, EAPS, Climate change, Global Warming, Climate, School of Science, Research, Antarctica, NASA, National Science Foundation (NSF)Solving the mystery of the Antarctic’s missing heathttps://news.mit.edu/2016/solving-the-mystery-antarctic-missing-heat-0617
New research may explain why sea temperatures around Antarctica haven’t risen as much as surface temperatures around the globe.Fri, 17 Jun 2016 17:00:01 -0400Lauren Hinkel | Oceans at MIThttps://news.mit.edu/2016/solving-the-mystery-antarctic-missing-heat-0617<p>Around the globe, ocean surface temperatures have been rising due to global warming, but the seas around Antarctica haven’t changed much. Now, researchers may have discovered why.</p>
<p>The world’s oceans have great potential to absorb and carry heat trapped in the atmosphere due to excess carbon emissions from human activities. Indeed, scientists have observed globally warming seas, particularly near the surface where the heat is entering from the atmosphere.</p>
<p>But the waters around Antarctica aren’t warming like the rest of the world’s oceans. Where the worldwide average sea surface temperature has increased by 0.08 degrees Celsius per decade since 1950, the Southern Ocean has barely felt a thing — only warming by 0.02 C and in some places, cooling. Scientists have been puzzled by this phenomenon, since the polar regions have been feeling disproportionately greater warming. While the Arctic is warming at twice the rate of the rest of the Earth, the waters around Antarctica remain cold, so much so that sea ice has actually grown in some regions.</p>
<p>Now, in a <a href="http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo2731.html" target="_blank">new <em>Nature Geoscience</em> study</a>, researchers from MIT and the University of Washington explain how upwelling from an ancient global ocean current could be the culprit for the Southern Ocean’s delayed warming.</p>
<p><strong>An oceanic conveyor belt</strong></p>
<p>Earth’s climate systems are adept at distributing resources around the globe that are necessary to support life; this includes the dispersal of heat energy. In most oceans, physical mixing of waters can help circulate heat into the ocean’s interior — a deep, cold-water reservoir ideal for storage. However, inherent features of the Southern Ocean serve to resist this process. As strong winds flow around Antarctica, they drive the ocean’s <a href="https://en.wikipedia.org/wiki/Antarctic_Circumpolar_Current" target="_blank">Antarctic circumpolar current (ACC)</a>. These currents then draw up deep waters from below to the surface adjacent to the continent, which is south of the ACC. Here, the Southern Ocean is generally stratified with cold, fresh waters on the surface overlaying warmer, salty waters — an atypical characteristic of the world’s seas. This also opposes the transfer of heat into the deep ocean. As a result, the heat absorbed should, more or less, stay near the surface; yet, surface of the Southern Ocean hasn’t been warming.</p>
<p>To track the fate of this excess heat, the team of scientists led by oceanographers <a href="http://oceans.mit.edu/JohnMarshall/" target="_blank">John Marshall</a>, the Cecil and Ida Green Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences (<a href="https://eapsweb.mit.edu/" target="_blank">EAPS</a>), and lead-author <a href="https://environment.uw.edu/faculty/kyle-armour/" target="_blank">Kyle Armour</a> from the University of Washington focused their attention on the Earth’s <a href="http://www.nature.com/ngeo/journal/v5/n3/full/ngeo1391.html" target="_blank">meridional overturning circulation (MOC)</a>.</p>
<p>This long, interhemispheric current behaves <a href="http://news.mit.edu/2012/southern-ocean-climate-0228" target="_blank">like a large conveyor belt</a>, connecting the water at the poles and the surface ocean with the deep sea through subduction and upwelling processes. In the Southern Ocean, upwelling dominates. After the water rises between Antarctica and the ACC, the current completes the loop by flowing back toward the equator, making its way to the Arctic where it later cools and sinks. Researchers Armour and Marshall suspected that this upwelling portion of the MOC could be dampening the warming, helping the Southern Ocean to remain cold, says Marshall.</p>
<p><strong>Following the heat</strong></p>
<p>To confirm their suspicions about the MOC’s role in this delayed warming, Armour and Marshall used a combination of observational data from <a href="http://www.bodc.ac.uk/projects/international/argo/southern_ocean/" target="_blank">Argo floats</a>, a global free-drifting ocean sampling array; ships; and satellites, along with circulation models to trace how the heat moved through the ocean. What they saw was a displacement of heat — not vertically into the deep ocean around Antarctica but horizontally over the surface of the ocean northward. The currents circulated the heat out of the Southern Ocean towards the equator. There, just north of the ocean’s Antarctic Circumpolar Current, Armour and Marshall observed significant warming, both in the surface and deep waters — a region known to mix and subduct water on a large scale.</p>
<p>“That was a key piece of evidence that showed it must be this meridional overturning circulation (MOC) at work,” Armour says.</p>
<p>What they found confirmed their suspicions. While strong westerly winds whip around Antarctica, they blow the warming surface water all around the continent northward toward the equator. At the same time, these winds draw up deep seawater, which replaces the water that’s flowing out of the Southern Ocean. However, this is not the only place that upwelling and water overturning occurs in the world’s seas. In some places like the west coast of the Americas, water is pulled up from a depth of a few hundred meters, but the water in the Southern Ocean is unique, rising from several thousand meters (close to 2 miles) below the surface.</p>
<p>“One way to think about this process is that the water that’s coming up in the Southern Ocean originated in the North Atlantic [where cold water sinks]. And it took a long time to trace the world’s oceans and then upwell. It’s very deep, old water, which hasn’t seen the effects of global warming,” Armour says. “And so, you constantly have this flux of old water toward the continent at depth. That water comes up to the surface and then flows northward, making up the overturning circulation.”</p>
<p>And as Marshall explains, “The reason that we think that surface temperatures don’t rise as much around Antarctica as they do in the north is because this old water is upwelling from depth and that quenches the warming signal [in the Southern Ocean].” This then leads to an influx of heat into surface waters because the atmosphere is continuing to warm while the Southern Ocean’s temperatures remain stable.</p>
<p>Other scientists have proposed alternative theories to try to explain this delayed warming. One is that climate change is causing glaciers to melt and more rain to fall over the Southern Ocean. This results in a freshening and cooling of surface waters, further stratifying the sea. But Armour and Marshall showed that this process isn’t large enough to cancel out the greenhouse gas warming effect. Another suggestion was that ozone depletion over Antarctica speeds up the westerly winds, driving water equatorward. Initially, this serves to cool the top ocean layer and expand sea ice, but ultimately, it enhances the overturning circulation — pulling warm water up at an increased rate, negating the observed Antarctic cooling.</p>
<p>Armour and Marshall then narrowed down the reason for the Southern Ocean’s delayed warming using models. They found that climate circulation models — which included both the ocean and the atmosphere — captured the observed warming well, and so they honed in on the ocean component, where they hoped to see the same effect.</p>
<p>“We were able to isolate the ocean-part of the story — controlling much more cleanly that which was going on in the atmosphere — and show that we got the same general patterns as in the observations,” says Marshall. This provided another clue that they were on the right track with the meridional overturning circulation. Lastly, the researchers added a passive tracer to the ocean models, which behaved like a surface injection of heat, but didn’t change the currents or water features, similar to dropping paper dots into a stream.</p>
<p>Each of these experiments produced the same result. “It’s not just the observations that show this [delayed warming]. We ran climate models and all of them tend to show a slower warming of the Southern Ocean. It eventually does warm up quite a bit, almost as much as the Arctic in fact, but it takes many, many centuries, even thousands of years to get there,” Armour states. Backed by this evidence, Armour and Marshall could say that the meridional overturning circulation was likely responsible for Southern Ocean’s behavior.</p>
<p>Armour was pleasantly surprised by how clean the answer turned out to be. “It was so robust through a huge range of complexity — starting from the climate systems, through very sophisticated climate models, all the way to very simple ocean-only models. This kind of robustness and simplicity was what we were hoping for, but it’s always surprising things work out this nicely.”</p>
<p>“I thought it [the study] was brilliant,” said <a href="http://www.goc411.ca/en/60012/John-Fyfe" target="_blank">John Fyfe</a>, a Senior Research Scientist with <a href="https://www.ec.gc.ca/cc/" target="_blank">Environment and Climate Change Canada</a>, who was not involved with the research. “I think it will become the textbook on the role that <a href="http://www.realclimate.org/index.php/archives/2004/11/anthropogenic-forcing/" target="_blank">anthropogenic forcing</a> [plays] in the pattern of ocean temperature changes in the Southern Ocean, which has been perplexing for some time.”</p>
<p>One of the takeaways, according to both Armour and Marshall, was the need to understand how differently the Arctic and Antarctic react to climate change. “You can’t directly compare the Arctic to the Antarctic when you’re talking about global warming because the greenhouse gas effect has occurred on top of very different background ocean circulations,” says Armour. “And that’s what we’re seeing here, the ocean circulation — on top of which global warming is happening — is really key in setting these [regional] patterns of warming.”</p>
<p><strong>Implications for Antarctic ice</strong></p>
<p>The next step is to evaluate if cooling surface waters around Antarctica could impact the Southern Ocean’s observed sea ice expansion and, if so, how. Marshall says that, overall, Antarctic sea ice isn’t significantly trending upward or down, but rather remaining constant.</p>
<p>Marshall and a recent MIT EAPS graduate <a href="https://paocweb.mit.edu/people/yavor-kostov" target="_blank">Yavor Kostov</a> PhD '16 postulate that stronger westerly winds around Antarctica could enhance this transport of heat northward, <a href="http://oceans.mit.edu/news/featured-stories/southern-ocean-cooling-in-a-warming-world" target="_blank">facilitating sea ice growth</a>. “The argument,” Armour says, “is that because of upwelling around Antarctica, the surface ocean hasn’t been warming very quickly, which means that, when you do change the winds, you could potentially explain the last several decades of cooling on top of this background of very slow warming.”</p>
Ocean surface temperature trends over the last 50 years. While the Arctic warms rapidly, the Southern Ocean around Antarctica has not warmed much, if at all. Image courtesy of the researchers.Oceans at MIT, EAPS, Research, Oceanography and ocean engineering, Climate, Climate change, Climate models, School of ScienceTracking Greenland’s ice melt with seismic waveshttps://news.mit.edu/2016/tracking-greenland-ice-melt-seismic-waves-0506
Technique uses vibrations generated by ocean waves to monitor ice sheet’s seasonal changes.Fri, 06 May 2016 13:59:59 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2016/tracking-greenland-ice-melt-seismic-waves-0506<p>Researchers from MIT, Princeton University, and elsewhere have developed a new technique to monitor the seasonal changes in Greenland’s ice sheet, using seismic vibrations generated by crashing ocean waves. The results, published today in the journal <em>Science Advances</em>, may help scientists pinpoint regions of the ice sheet that are most vulnerable to melting. The technique may also set better constraints on how the world’s ice sheets contribute to global sea-level changes.</p>
<p>“One of the major contributors to sea level rise will be changes to the ice sheets,” says Germán Prieto, the Cecil and Ida Green Career Development Assistant Professor in the Department of Earth, Atmospheric and Planetary Sciences (EAPS) at MIT. “With our technique, we can continuously monitor ice sheet volume changes associated with winter and summer. That’s something that global models need to be able to take into account when calculating how much ice will contribute to sea level rise.”</p>
<p>Prieto and his colleagues study the effects of “seismic noise,” such as ocean waves, on the Earth’s crust. As ocean waves crash against the coastline, they continuously create tiny vibrations, or seismic waves.</p>
<p>“They happen 24 hours a day, seven days a week, and they generate a very small signal, which we generally don’t feel,” Prieto says. “But very precise seismic sensors can feel these waves everywhere in the world. Even in the middle of continents, you can see these ocean effects.”</p>
<p>The seismic waves generated by ocean waves can propagate through the Earth’s crust, at speeds that depend in part on the crust’s porosity: The more porous the rocks, the slower seismic waves travel. The scientists reasoned that any substantial overlying mass, such as an ice sheet, may act like a weight on a sponge, squeezing the pores closed or letting them reopen, depending on whether the ice above is shrinking or growing in size.</p>
<p>The team, led by Aurélien Mordret, a postdoc in EAPS, hypothesized that the speed of seismic waves through the Earth’s crust may therefore reflect the volume of ice lying above.</p>
<p>“By looking at velocity changes, we can make predictions of the volume change of the ice sheet mass,” Prieto says. “We can do this continuously over time, day by day, for a particular region where you have seismic data being recorded.”</p>
<p><strong>Short track</strong></p>
<p>Scientists typically track changing ice sheets using laser altimetry, in which an airplane flies over a region and sends a laser pulse down and back to measure an ice sheet’s topography. Researchers can also look to data gathered by NASA’s GRACE (Gravity Recovery and Climate Experiment) mission — twin satellites that orbit the Earth, measuring its gravity field, from which scientists can infer an ice sheet’s volume.</p>
<p>As Prieto points out, “you can only do laser altimetry several times a year, and GRACE satellites require about one month to cover the Earth’s surface.”</p>
<p>In contrast, ocean waves and the seismic waves they produce generate signals that sensors can pick up continuously.</p>
<p>“This has very good time resolution, so it can look at melting over short time periods, like summer to winter, with really high precision that other techniques might not have,” Prieto says.</p>
<p><strong>Seismic shakeup</strong></p>
<p>The researchers looked through seismic data collected from January 2012 to January 2014, from a small seismic sensor network situated on the western side of Greenland’s ice sheet. The sensors record seismic vibrations generated by ocean waves along the coast, and they have been used to monitor glaciers and earthquakes. Prieto’s team is the first to use seismic data to monitor the ice sheet itself.</p>
<p>Looking through the seismic data, the scientists were able to detect incredibly small changes in the velocity of seismic waves, of less than 1 percent. They tracked average velocities from January 2012 to 2014, and observed very large seismic velocity decreases in 2012, versus 2013. These measurements mirrored the observations of ice sheet volume made by the GRACE satellites, which recorded abnormally large melting in 2012 versus 2013. The comparison suggested that seismic data may indeed reflect changes in ice sheets.</p>
<p>Using data from the GRACE satellites, the team then developed a model to predict the volume of the ice sheet, given the velocity of the seismic waves within the Earth’s crust. The model’s predictions matched the satellite data with 91 percent accuracy.</p>
<p>Nikolai Shapiro, research director for the National Center for Scientific Researchat the Institute de Physique du Globe de Paris, sees the group’s technique as “a very nice contribution in the direction of developing methods for environmental seismological monitoring.” He adds that such use of seismic data to study ice sheets &nbsp;“will certainly become more and more frequent and will become even more valuable, with an ongoing effort to install seismic networks in the vicinity of ice sheets, both in southern and northern polar areas.”</p>
<p>Toward that end, the team plans next to use available seismic networks to track the seasonal changes in the Antarctic ice sheet.</p>
<p>“Our efforts right now are to use what’s available,” Prieto says. “Nobody has been looking at this particular area using seismic data to monitor ice sheet volume changes.”</p>
<p>If the technique is proven reliable in Antarctica, Prieto hopes to stimulate a large-scale project involving many more seismic sensors distributed along the coasts of Greenland and Antarctica.</p>
<p>“If you have very good coverage, like an array with separations of about 70 kilometers, we could in principle make a map of the regions that have more melting than others, using this monitoring, and maybe better refine models of how ice sheets respond to climate change,” Prieto says.</p>
<p>In addition to MIT and Princeton, the paper’s contributing institutions are Stanford University, Harvard University, and Boise State University. This research was supported, in part, by the National Science Foundation.</p>
A photo of the edge of the Greenland ice sheet. “With our technique, we can continuously monitor ice sheet volume changes associated with winter and summer,” Germán Prieto says.Climate, Climate change, Oceanography and ocean engineering, Research, School of Science, EAPS, Earth and atmospheric sciences, NASA, National Science Foundation (NSF)Study: Ancient tectonic activity was trigger for ice ageshttps://news.mit.edu/2016/ancient-tectonic-activity-was-trigger-for-ice-ages-0418
Continental shifting may have acted as a natural mechanism for extreme carbon sequestration. Mon, 18 Apr 2016 15:00:00 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2016/ancient-tectonic-activity-was-trigger-for-ice-ages-0418<p>For hundreds of millions of years, Earth’s climate has remained on a fairly even keel, with some dramatic exceptions: Around 80 million years ago, the planet’s temperature plummeted, along with carbon dioxide levels in the atmosphere. The Earth eventually recovered, only to swing back into the present-day ice age 50 million years ago.</p>
<p>Now geologists at MIT have identified the likely cause of both ice ages, as well as a natural mechanism for carbon sequestration. Just prior to both periods, massive tectonic collisions took place near the Earth’s equator — a tropical zone where rocks undergo heavy weathering due to frequent rain and other environmental conditions. This weathering involves chemical reactions that absorb a large amount of carbon dioxide from the atmosphere. The dramatic drawdown of carbon dioxide cooled the atmosphere, the new study suggests, and set the planet up for two ice ages, 80 million and 50 million years ago.</p>
<p>“Everybody agrees that on geological timescales over hundreds of millions of years, tectonics control the climate, but we didn’t know how to connect this,” says Oliver Jagoutz, associate professor of Earth, Atmospheric and Planetary Sciences (EAPS) at MIT. “I think we’re the first ones to really link large-scale tectonic events to climate change.”</p>
<p>Jagoutz and his colleagues, EAPS Professor Leigh Royden, and Francis Macdonald of Harvard University, have published their findings today in the <em>Proceedings of the National Academy of Sciences</em>.</p>
<p><strong>Putting the squeeze on</strong></p>
<p>The two tectonic collisions that the team studied stemmed from the same event: the slow northward migration of Gondwana, a supercontinent that spanned the Southern Hemisphere from 300 million to 180 million years ago and eventually broke up to form Antarctica, South America, Africa, India, and Australia.</p>
<p>Around 180 million years ago, tectonic activity began to push fragments of Gondwana up toward the northern supercontinent of Eurasia, which slowly squeezed and eventually closed the Neo-Tethys Ocean, an ancient body of water lying between the supercontinents.</p>
<p>In previous work, Jagoutz and his colleagues developed a model to simulate the tectonic shifting that occurred in and around that ocean as Gondwana fragments were crushed against Eurasia. Through analysis of ancient rocks in today’s Himalayas, the team determined a sequence of events as the continents merged.</p>
<p>They found that 90 million years ago, the northeastern edge of the African plate collided and slid under an oceanic plate in the Neo-Tethys Ocean, creating a chain of volcanoes. At 80 million years ago, as Africa continued advancing north, the oceanic plate was pushed further up and over the continent, exposing ocean rock to the atmosphere, while simultaneously terminating the volcanoes. Then, 50 million years ago, India merged with Eurasia in a second collision in which a different region of the oceanic plate was pushed up onto that continent.</p>
<p>Both collisions took place in the Intertropical Convergence Zone (ITCZ), an atmospheric region hovering over the Earth’s equator, in which trade winds come together to generate a region of intense temperatures and rainfall.</p>
<p><strong>A weathering trigger</strong></p>
<p>For this new paper, the researchers wondered whether the tectonic collisions in this extremely tropical region may have played a part in pulling huge amounts of carbon dioxide out of the atmosphere and triggering the ice ages.</p>
<p>Certain types of rock, if exposed to high heat and heavy rain, undergo chemical reactions and effectively absorb carbon dioxide, a process known as silicate weathering. These rocks include basalts and “ultramafic” rocks, which are often found within oceanic plates. If these rocks are exposed to the atmosphere in a tropical region, they can act as very efficient carbon sinks.</p>
<p>The team hypothesized that the two collisions, involving Africa and then India, brought basaltic and ultramafic rocks up from the oceans and onto land, creating carbon sinks 80 and 50 million years ago. Both collisions also effectively turned off carbon sources by burying volcanoes that had been emitting carbon dioxide and other gases into the atmosphere.</p>
<p>To know whether such a sequence of events directly reduced carbon dioxide in the atmosphere, the researchers looked to weathering rates of different rock types, including granites, basalts, and ultramafics. These rates, which have been calculated by other researchers, describe the way rocks erode and take up carbon dioxide, given exposure to a certain amount of rainfall.</p>
<p>They then applied these weathering rates to their model’s estimates of the amount of oceanic plate that was pushed up onto Africa and India, at 80 and 50 million years ago, respectively. After determining the amount of carbon dioxide sequestered by these rocks, they calculated the total amount of atmospheric carbon dioxide through time, from 100 million years ago to around 40 million years ago.</p>
<p>The team found that carbon dioxide dipped dramatically at precisely the time the two collisions occurred. The levels of carbon dioxide also mirrored the temperature of the oceans during this interval.</p>
<p>Jagoutz says one reason these two collisions had such an extreme effect on atmospheric carbon dioxide may have been the fact that each continent continued moving north, exposing new basaltic and ultramafic material, “like a bulldozer that brings fresh rock to the surface.”</p>
<p>Interestingly, a similar process is taking place today, albeit at a smaller scale, near the island of Java. The same tectonic activity that shifted Gondwana northward more than 100 million years ago is today pushing the Australian plate north, and as a result, is piling up basaltic material on Java within the ITCZ, which Jagoutz says is “a huge carbon sink.”</p>
<p>“What nature shows us is, if you put a lot of these rocks in the tropics, where it’s hot, muggy, wet, and rains every day, and you also have the effect of removing the soil constantly by tectonics and thus exposing fresh rocks, then you have an excellent trigger for ice ages,” Jagoutz says. “But the question is whether that is a mechanism that works on the timescale that is relevant for us.”</p>
<p>“To confidently estimate the long-term fate of fossil fuel carbon in the atmosphere, we need to fully understand the dynamics of the carbon cycle and how it operates on all time scales,” says Lee Kemp, professor of geosciences at Penn State University. “This study highlights an important restorative force of the carbon cycle. The ‘repair mechanism’ for volcanism-induced warming is the chemical weathering of the volcanic rocks themselves — a repair job that takes millions of years.”</p>
“Everybody agrees that on geological timescales over hundreds of millions of years, tectonics control the climate, but we didn’t know how to connect this,” says Oliver Jagoutz.Image: Christine Daniloff/MITClimate, Climate change, Geology, Earth and atmospheric sciences, Environment, Oceanography and ocean engineering, Research, EAPS, School of ScienceKoichi Masubuchi, professor emeritus of ocean engineering, dies at 92https://news.mit.edu/2016/koichi-masubuchi-professor-emeritus-ocean-engineering-dies-0413
Masubuchi, a leading expert on welding science and fabrication technology, also started the Japanese Language School.Wed, 13 Apr 2016 12:00:01 -0400Alissa Mallinson | Department of Mechanical Engineeringhttps://news.mit.edu/2016/koichi-masubuchi-professor-emeritus-ocean-engineering-dies-0413<p>Koichi Masubuchi, professor emeritus of ocean engineering, passed away on April 1 at the age of 92 in Concord, Massachusetts.&nbsp;</p>
<p>Masubuchi was a leading expert in welding science and fabrication technology whose work helped to progress the understanding of welding and the important role it plays in marine and aerospace structures.&nbsp;</p>
<p>Born in Otaru, Japan, in 1924, Masubuchi served in the Japanese Navy during World War II as a ship fitter in a naval shipyard. He earned a bachelor's degree and a master’s degree from the University of Tokyo, both in naval architecture, and received a PhD in engineering from Tokyo University. He worked for five years as the chief of design and fabrication in the welding division of the Transportation Technical Research Institute in Tokyo before taking leave to serve in several different positions at the Battelle Memorial Institute in Ohio until 1962. In 1963, he moved back to Ohio to serve at Battelle Memorial Institute once again until 1968, when he started as an associate professor of naval architecture at MIT. &nbsp;In 1971, he was promoted to professor in the Department of Ocean Engineering, which later became part of the Department of Mechanical Engineering. He retired from MIT in 2001.&nbsp;</p>
<p>Masubuchi was interested in welding from a young age and spent most of his career at Batelle and MIT dedicated to progressing the science and engineering of welding fabrication. He spent his first 10 years at MIT focused on solving welding problems NASA was having with its Apollo project. During his 50 years conducting research on welding technology, Masubuchi authored or co-authored more than 220 papers and supervised more than 130 theses. His main areas of expertise were in the heat flow, residual stresses, and distortion in weldments; the fracture of welded structures; and the welding technologies for underwater and space applications.&nbsp;</p>
<p>Masubuchi served as president of the Japanese Association of Greater Boston from 1972 until 1981, and he started the Japanese Language School in 1975.&nbsp;</p>
<p>He was a fellow of the American Welding Society and received the Order of Sacred Treasure Gold Rays with Neck Ribbon from the Government of Japan for advancing welding technology and promoting friendship between Japan and the United States.&nbsp;</p>
<p>Masubuchi was also a member of the Society of Naval Architects and Marine Engineers, the American Society of Mechanical Engineers, ASM International, the Marine Technology Society, the Society of Experimental Stress Analysis, and the Society of Naval Architects of Japan.&nbsp;</p>
<p>Individuals wanting to make a donation in Masubuchi’s memory may send gifts to the Masubuchi Fund c/o Japanese Language School of Greater Boston at 792 Massachusetts Ave., Arlington, MA 02476. The fund was established to support the Japanese Language School of Greater Boston in honor of Masubuchi.</p>
Faculty, Obituaries, Mechanical engineering, Oceanography and ocean engineering, Fabrication, JapanDNA markers tell the story of deep sea adaptationhttps://news.mit.edu/2016/dna-markers-tell-story-deep-sea-adaptation-0318
Santiago Herrera studies the genome to establish new connections between species living in the deep sea.Fri, 18 Mar 2016 18:00:00 -0400Jennifer Cherone | Department of Biologyhttps://news.mit.edu/2016/dna-markers-tell-story-deep-sea-adaptation-0318<p>When you think about the deep sea, you might conjure up an image of the angler fish as portrayed in <em>Finding Nemo</em> or the white whale in <em>Moby Dick</em> — in short, you might envision a dark, mysterious, terrifying world miles beneath the surface where we live.</p>
<p>The deep sea, defined as everything that is 200 meters (or 60 stories) below sea level, makes up more than 95 percent of the world’s habitable space, yet it is indeed mysterious — we know very little about these aquatic habitats.</p>
<p>Santiago Herrera, a recent graduate of the MIT-Woods Hole Oceanographic Institution joint program, spent his PhD studying humanity's impact on the deep sea.</p>
<p>Growing up in Columbia, Herrera has been passionate about marine biology since he was a child. He has seen the impact that human activity can leave on the world around us, and, through his passion for the ocean, is driven to better understand how incidents of wide-spread pollution and overfishing may also leave a mark on the deep sea.</p>
<p>The deep sea is more sensitive to damage because organisms grow and reproduce at a much slower rate than organisms in shallower water or on land. The orange roughy fish, for example, cannot reproduce until it reaches the age of thirty. Recovery of these ecosystems would take many times that of land organisms.</p>
<p>Herrera has faced many hurdles in studying the deep sea. "It’s a big challenge because we don’t have a good inventory of species that live there yet," he says. Scientists rely on what can be collected with a net or captured on video by a submersible for only a few minutes, making it nearly impossible to objectively classify a new species.</p>
<p>However, Herrera has helped transform the way that we think of species in the deep sea by integrating new DNA data with existing paleontological, geological, and oceanographical information. He developed a new toolset of DNA markers — pieces of the genome that are used to establish differences between individuals — to unambiguously determine what makes two species different.</p>
<p>"I think of genes as if they were books in a library," he says. "They have a certain amount of information, and can tell you something about the history of that individual. Two different books are not going to tell the same history; they can tell different histories. So the more genes you sample, the more books you read ... the closer you get to understanding what really happened and to be much more certain and confident on the interpretations and the results that you get"</p>
<p>One of Herrera’s favorite deep sea habitats is hydrothermal vents — mineral rich hot springs that were discovered in 1977 by the famed submersible <em>Alvin</em>. Barnacles, a kind of crustacean most commonly found attached to hard surfaces like piers, boats, and rocks, also take up residence in hydrothermal vents far below the surface of the ocean. In fact, barnacles are one of the most common inhabitants of hydrothermal vent ecosystems worldwide.</p>
<p>Herrera examined the genes of barnacles living in many different areas. He discovered that these genes — or "books" — all told the same biographical story. Had they evolved separately, their stories would have been very different from one another. Thus, he hypothesizes that the barnacles are able to disperse larvae over distances up to hundreds of kilometers (comparable to the distance between Boston and New York City). Once there, the young barnacles are able to survive the conditions of this new home, including sizeable differences in ocean depth. Such adaptability is a good indicator of hardiness in the face of changing environmental conditions imposed by human activities.</p>
<p>Herrera also examined the DNA of many coral samples, which revealed apparent mutations, or changes in the DNA, that allowed them to thrive in new environments. These mutations repeatedly appear in different areas with the same environmental conditions, implying that these coral all evolved the same genetic change in response to the condition. Ongoing research seeks to determine the molecular mechanisms triggered by these genetic mutations that allow deep sea coral to adapt to new environments. Knowing the molecular adjustments that coral naturally make in different ocean conditions could help researchers further study coral’s survival through global warming.</p>
<p>By further comparing the DNA of additional samples of barnacles and coral, Herrera ascertained information about where and when these species originally evolved and then dispersed. Combining his research with existing paleontological data, he observed a common dispersal at the end of the Cretaceous period (when the dinosaurs went extinct), out of the Western Pacific through the southern hemisphere, that matches the ocean currents of the time. Herrera even found similar evolutionary patterns to groups of organisms outside of the deep sea that originated around the same time, meaning a common set of conditions drove biodiversity both on land and in the sea. Thus, Herrera believes life on the surface of the ocean and in the deep sea are more connected than the vast distance may suggest.</p>
<p>This interconnectedness between land and sea plays out to this day in interactions between coral, the biodiversity they support, and human recreation and consumption. The impacts of damage to shallow water coral are already well known. However, the deep sea contains nearly two thirds of all known coral species, making it the primary home for the majority of coral biodiversity. Human activities are imposing an increasingly imminent environmental threat to these ocean flora and fauna. With corals being some of the oldest living organisms, reaching up to 4,000 years old, they will not be easy to replace. Herrera says, “Out of sight should not be out of mind.”</p>
<p>When asked what advice he would give to a student just entering the field, Herrera replied, “Come armed with a skill outside of oceanography … like molecular biology, genetics, computer science, or math. Those will be very important tools to bring in new ideas.”</p>
<p>Herrera has helped pioneer the use of genomics to study the deep sea. He is now a postdoc at the University of Toronto in Canada where he studies human epigenetics, looking at the link between environment and disease. Epigenetics is not a well-developed topic in ocean science. Herrera hopes to take this time to gain a new skillset that he can eventually bring back to the field of oceanography that will help him to look at questions in marine science in new and different ways.&nbsp;</p>
Clockwise from top left: Santiago Herrera (far left) leads an exploration dive of the ROV Little Hercules in the deep Celebes Sea in 2010; Herrera examines a specimen of a species of colonial salps found in a New Zealnd Kelp forest in 2012; Herrera (left) and Andrea Quattrini (right) store specimens of deep sea corals collected with WHOI's ROV Jason in 2009; and stalked barnacles from the vent fields at the Kawio Barat volcano in the Western Pacific.Barnacles image courtesy of NOAA Okeanos Explorer Program, INDEX-SATAL 2010School of Science, Oceanography and ocean engineering, Woods Hole, Biology, Students, Profile, Genetics, DNAWhales dine with their own kindhttps://news.mit.edu/2016/whales-feed-species-specific-hotspots-0302
Mapping whale calls, researchers find the predators feed in species-specific hotspots.Wed, 02 Mar 2016 12:59:59 -0500Jennifer Chu | MIT News Officehttps://news.mit.edu/2016/whales-feed-species-specific-hotspots-0302<p>For a few weeks in early fall, Georges Bank — a vast North Atlantic fishery off the coast of Cape Cod — teems with billions of herring that take over the region to spawn. The seasonal arrival of the herring also attracts predators to the shallow banks, including many species of whales.</p>
<p>Now researchers from MIT, Northeastern University, the Institute of Marine Research in Norway, and the National Oceanic and Atmospheric Administration, have found that as multiple species of whales feast on herring, they tend to stick with their own kind, establishing species-specific feeding centers along the 150-mile length of Georges Bank. The team’s results are published today in the journal <em>Nature.</em></p>
<p>Based on acoustic data they collected in the region in 2006, the researchers identified and mapped the calls of various whales, and discovered a clear grouping of species within the dense herring shoals: Humpback whales congregated in two main clusters, at either end of the spawning grounds, while minke, fin, and blue whales set up feeding territories in the space in between.</p>
<p>In general, calls from each whale species increased dramatically at nighttime, when herring tended to form extremely dense shoals. During the day, these whale calls dissipated, as herring scattered throughout the seafloor.</p>
<p>These results represent the first time that scientists have observed such predator and prey interactions over a large marine region.</p>
<p>“It’s known that different marine mammal species will eat fish, but no one has mapped their simultaneous feeding distributions over these huge scales,” says Purnima Ratilal PhD ’02, associate professor of electrical and computer engineering at Northeastern University. “Maybe there is some territorialism going on, or maybe they are preferentially selecting these locations based on their different foraging mechanisms. That’s material for new research.”</p>
<p>Ratilal and her husband, Nicholas Makris, professor of mechanical engineering at MIT, along with their students, are co-authors of the paper.</p>
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<p><strong>Fishing for sound</strong></p>
<p>In 2006, Makris and Ratilal led a two-week cruise to Georges Bank, initially to track and study the behavior of populations of herring, which can number in the billions within a single shoal. The team had developed a remote-sensing system that uses acoustics to instantaneously image and continuously monitor fish populations over &nbsp;tens of thousands of square kilometers. Unlike conventional technologies, their system uses the ocean as a waveguide through which acoustic waves can travel over much greater distances, to sense the marine environment.</p>
<p>To get a much wider, more detailed view of the herring populations, Makris and Ratilal deployed 160 hydrophones during their 2006 cruise, towing the array, like a “big acoustic antenna,” in and around Georges Bank. Using their ocean acoustic waveguide sensing technique, they mapped the evolving shoals over the two-week period in October.</p>
<p>During that cruise, the group remembers hearing distinct sounds coming through &nbsp;the ship’s hull.</p>
<p>“We were hearing these strange haunting sounds in the galley, like an upsweep, then a down-sweep,” Makris recalls. “Purnima recognized these were whale calls, and had all the characteristics of a classic humpback song. At that point she started the research that led to the current paper in <em>Nature</em>, which she spearheaded.”</p>
<p>Makris notes that such whale calls have been heard through the hulls of ships for thousands of years.</p>
<p>“The Patogonian Indians even had a name for them: 'Yakta,’” Makris says. “People had been listening to these sounds for a very long time, and it’s really this century that we’re starting to localize and observe their behavior.”</p>
<p><strong>Hearing hotspots in the night</strong></p>
<p>The group continued looking through the data, even after they had analyzed them for herring signals, to look this time for whale calls. The team developed a technique to sift through the acoustic data for interesting signals — a method called passive ocean acoustic waveguide remote sensing (POAWRS).</p>
<p>Through the years, the team gathered research on the characteristics of certain whale species’ calls and looked for these characteristics in their acoustic data. They eventually identified several hundred thousand calls, mostly along the northern edge of Georges Bank.</p>
<p>“Different marine mammals in the ocean produce different sounds, sort of related to their size,” Ratilal says. “Humpbacks have a distinct song, while some species of tooth whales can sound like birds chirping.”</p>
<p>“Fin whale calls, on the other hand, are in the register of a bass guitar,” Makris adds.</p>
<p>The researchers &nbsp;located the source of each call by triangulation and other methods unique to waveguides, and found that the call rates of four main species of whales observed — humpback, sei, minke, and blue — tended to go up significantly at night, possibly in response to the increasing number of herring.</p>
<p>“Spawning herring typically don't form big shoals during daytime because it’s too risky they can get caught more easily,” Makris notes. “So they form just as the sun goes down. That’s when the whale calls start going wild and begin to come from on top of the shoals.”</p>
<p>These calls were concentrated in species-specific “hotspots,” with humpback whale calls bookending the other three species, all along the northern length of Georges Bank.</p>
<p>The group found that humpbacks in particular emitted a distinct pattern of calls that may indicate a cooperative feeding ritual, which others have observed.</p>
<p>“The whales will circle the herring, and then one will blow a bubble to contain the fish group, and another will scream and scare the fish into a tight ball,” Ratilal says. “Then another will give a signal, and they’ll all come up with their jaws open.”</p>
<p>Jeff Simmen executive director of the Applied Physics Laboratory at the University of Washington, says that for the most part, technologies used to observe marine ecosystems are unable to localize fish and marine mammals at the same time. In contrast, Makris and Ratilal’s approach “provides unusual insight into the macroscopic behavior of marine populations.”</p>
<p>“In short, the methodology provides a new and grand view of marine populations that will lead to completely new perspectives about the marine ecosystem, perhaps in a similar way that the enhanced views from the Hubble Space Telescope have changed our perspectives on the universe,” Simmen says.</p>
<p>Going forward, the team hopes to tease out more marine behaviors in their dataset.</p>
<p>“With this technology, you can really sense a lot of things,” Makris says. “Fish and marine mammals are just two examples.” Ratilal adds, “There are quite a few other interesting &nbsp;phenomena in our dataset.”</p>
<p>This research was supported, in part, by the Ocean Acoustics Program of the Office of Naval Research, the National Science Foundation, the National Oceanographic Partnership Program, the Alfred P. Sloan Foundation, and is a contribution to the Census of Marine Life.</p>
Using acoustic data, researchers identified and mapped the calls of diverse marine mammal species in fish spawning grounds on Georges Bank, including (from top right, clockwise): blue (snout only is pictured), humpback, orca, fin, dolphin, sei, pilot, sperm, and minke.
Illustration: Jordan Beckvonpeccoz (with input from Purnima Ratilal and Nicholas C. Makris) Environment, Oceanography and ocean engineering, Ocean science, Biology, Animals, Research, Department of Mechanical Engineering, School of Engineering, National Science Foundation (NSF)New theory of deep-ocean sound waves may aid tsunami detectionhttps://news.mit.edu/2016/deep-ocean-sound-waves-may-aid-tsunami-detection-0301
Surface waves can trigger powerful sound waves that race through the deep ocean, study suggests.Tue, 01 Mar 2016 00:00:00 -0500Jennifer Chu | MIT News Officehttps://news.mit.edu/2016/deep-ocean-sound-waves-may-aid-tsunami-detection-0301<p>Acoustic-gravity waves are very long sound waves that cut through the deep ocean at the speed of sound. These lightning-quick currents can sweep up water, nutrients, salts, and any other particles in their wake, at any water depth. They are typically triggered by violent events in the ocean, including underwater earthquakes, explosions, landslides, and even meteorites, and they carry information about these events around the world in a matter of minutes.</p>
<p>Researchers at MIT have now identified a less dramatic though far more pervasive source of acoustic-gravity waves: surface ocean waves, such as those that can be seen from a beach or the deck of a boat. These waves, known as surface-gravity waves, do not travel nearly as fast, far, or deep as acoustic-gravity waves, yet under the right conditions, they can generate the powerful, fast-moving, and low-frequency sound waves.</p>
<p>The researchers have developed a general theory that connects gravity waves and acoustic waves. They found that when two surface-gravity waves, heading toward each other, are oscillating at a similar but not identical frequency, their interaction can release up to 95 percent of their initial energy in the form of an acoustic wave, which in turn carries this energy and travels much faster and deeper.</p>
<p>This interaction may occur anywhere in the ocean, in particular in regions where surface-gravity waves interact as they reflect from continental shelf breaks, where the deep-sea suddenly faces a much shallower shoreline.</p>
<p>Usama Kadri, a visiting assistant professor and a research affiliate in MIT’s Department of Mathematics, says the team’s results establish a concrete and detailed relationship between surface-gravity waves and acoustic-gravity waves, which, until now, scientists had suspected did not exist. Understanding this relationship, he says, allows researchers to describe how energy is exchanged between gravity and acoustic waves. He says this energy could be vital for many marine life forms, and it could play a role in water transport and the redistribution of carbon dioxide and heat to deeper waters, thereby sustaining a healthy marine environment.</p>
<p>Kadri and his colleague, Triantaphyllos Akylas, a professor of mechanical engineering at MIT, have published their results in the <em>Journal of Fluid Mechanics.</em></p>
<p><strong>Adjusting for the real world</strong></p>
<p>For the most part, gravity waves and acoustic waves have been regarded as completely separate entities, one having no effect on the other. That’s because their properties are so different, in both length and timescales. While gravity is the main force acting to restore and stabilize surface-gravity waves (hence the name), its effect on sound waves is negligible. On the other hand, the fact that water is slightly compressible is what allows pressure waves, such as sound, to travel through, though this property has almost no effect on surface waves.</p>
<p>Kadri says the typical water wave equations used to characterize ocean wave interactions do not apply to acoustic-gravity waves, as they do not factor in compressibility and gravity effects.</p>
<p>“Without compressibility and gravity, we cannot describe low-frequency sound waves correctly,” Kadri says. “This is one of the reasons why researchers have mostly overlooked acoustic-gravity waves.”</p>
<p>Kadri derived a wave equation that includes compressibility and gravity as well as higher-order nonlinear terms.</p>
<p>“In linear theory, two surface-gravity waves traveling toward each other do not feel each other; they get closer, pass each other, and then move away without exchanging any form of energy, as if they have never met,” Kadri explains. “However, in reality the picture is more complicated, and nonlinear effects may come into play, resulting in energy exchange and even generation of new waves, sometimes. Here, at specific frequency ranges, gravity waves can actually produce an acoustic wave that has completely different properties — and that is amazing.”</p>
<p><strong>Rolling in the deep</strong></p>
<p>The newly derived wave equation allowed Kadri to study the behavior of both acoustic and gravity waves. He analyzed the theoretical interactions within a wave triad consisting of two surface-gravity waves and one acoustic-gravity wave. In 2013, he proved numerically that this configuration of waves should resonate, or exchange energy, meaning that as two of the three waves oscillate, they should drive the third wave to oscillate in response. Now, using the modified wave equation, along with multiple scales analysis, he derived what are called “evolution equations” to describe how the amplitudes of all three waves change as they exchange energy.</p>
<p>Surprisingly, he calculated that if two surface waves flow toward each other at roughly the same frequency and amplitude, as they meet and roll through each other the majority of their energy — up to 95 percent — can be turned into a sound wave, or acoustic-gravity wave. This energy can fluctuate, depending on the initial amplitudes and frequencies of the surface-gravity waves. Even when the surface-gravity waves travel in the form of short bursts, they can still transfer over 20 percent of their energy to acoustic-gravity waves, an amount that cannot be neglected. &nbsp;</p>
<p>“This is incredible, just to think that these waves are so different,” Kadri says. “Having them sharing energy is really exciting; this explains how some of the energy that comes from the atmosphere, from the sun and the wind, to the upper part of the ocean, can actually be driven to roll in the deep ocean through acoustic-gravity waves.”</p>
<p>Kadri says the results may help scientists connect interactions between not only surface and deep ocean waters, but also with the atmospheric forces that affect surface waves.</p>
<p>Now Kadri is imparting this new understanding of wave interactions to a critical application: tsunami detection. He is working with the Woods Hole Oceanographic Institution to design a system to detect acoustic-gravity waves that precede a tsunami, traveling more than 10 times as fast as the more destructive wave.&nbsp;</p>
<p>“Severe sea states, such as tsunamis, rogue waves, storms, landslides, and even meteorite fall, can all generate acoustic-gravity waves,” Kadri says. “We hope we can use these waves to set an early alarm for severe sea states in general and tsunamis in particular, and potentially save lives.”</p>
“Without compressibility and gravity, we cannot describe low-frequency sound waves correctly,” Usama Kadri says. “This is one of the reasons why researchers have mostly overlooked acoustic-gravity waves.” Illustration: Christine Daniloff/MITClimate, Earth and atmospheric sciences, Energy, Environment, Mathematics, Ocean science, Oceanography and ocean engineering, Physics, Research, Tsunami, School of ScienceGreen eelgrass, blue carbonhttps://news.mit.edu/2016/green-eelgrass-blue-carbon-0229
MIT Sea Grant is working with several partners to quantify the carbon storage of eelgrass beds in Massachusetts.Mon, 29 Feb 2016 16:12:01 -0500Kathryn Baltes | MIT Sea Granthttps://news.mit.edu/2016/green-eelgrass-blue-carbon-0229<p>By understanding the role that eelgrass ecosystems play in preparing for and mitigating the effects of climate change we can better make the case for securing protection and restoration resources.</p>
<p>Seagrasses are aquatic plants, marine grasses that evolved on land with other grasses and later migrated back to the coastal ocean. Our local species here in Massachusetts is eelgrass, or <em>Zostera marina</em>. If you look closely, eelgrass resembles the grass from your lawn, with long flat blades, shallow roots and flowers.</p>
<p>Eelgrass beds spread out and form meadows, which help tie down sediments, improving water clarity and reducing shoreline erosion. Just like a terrestrial meadow, eelgrass meadows are teeming with life. They provide a safe place for marine animals to lay eggs, a nursery habitat for young fish, and protection from predators for young animals like scallops, crabs, and lobsters. Eelgrass meadows also play an important part in improving water quality by recycling nutrients in runoff from land.</p>
<p>More recently, seagrass beds in tropical regions have been recognized as an important natural carbon sink, storing a large amount of carbon in both the plant tissue and in the sediments the beds help collect. Carbon storage and sequestration by coastal marine ecosystems, often called "blue carbon," is best understood in habitats such as mangroves, salt marshes and seagrass meadows. The carbon storage capacity of seagrass meadows is the least well quantified of these coastal habitats. Very little is known about the capacity of eelgrass meadows in temperate regions, like the Northeast.</p>
<p>MIT Sea Grant is working with the Environmental Protection Agency (<a href="http://www.epa.gov/aboutepa/epa-region-1-new-england" target="_blank">EPA</a>), researchers at <a href="http://sites.bu.edu/novak/" target="_blank">Boston University</a>, the <a href="http://www.mass.gov/eea/agencies/dfg/dmf/" target="_blank">Massachusetts Division of Marine Fisheries</a>, and the <a href="http://www.mass.gov/eea/agencies/mass-bays-program/" target="_blank">Massachusetts Bays National Estuary Program</a> (MassBays) to conduct studies to quantify the carbon storage of eelgrass beds in coastal Massachusetts. Field surveys were done during summer months in the height of the eelgrass growing season, from five eelgrass beds in Massachusetts. Divers suited up to take sediment cores inside and outside eelgrass meadows and collected samples of eelgrass. A shore team set up under an umbrella to process the cores, water samples, and plant tissues as the divers brought them up. Blade characteristics such as length, presence of seeds, and presence of invasive tunicates were recorded. Samples were then packed up and sent to labs for analysis.</p>
<p>The study found that eelgrass meadows in coastal waters around Massachusetts hold the same amount of carbon or more as researchers have documented in other studies in and around the North Atlantic. Unsurprisingly, the study also gave some key evidence to support the common knowledge that sediment in eelgrass beds has more carbon than sediments without eelgrass cover. Stable isotope analysis of the sediment gave fascinating insights into just where the carbon that is being held comes from. Initial analysis identified that the carbon originates from both the eelgrass plants themselves, and, perhaps more importantly, also from phytoplankton and other floating particles in the water. This means that eelgrass meadows have the capacity to capture and store carbon from outside sources, increasing the potential amount of carbon they are able to sequester to more than what the meadows produce.</p>
<p>These results offer insight into the important ecosystem services eelgrass meadows provide. The study also has the potential to make significant impacts in how regulatory agencies view eelgrass meadows. As a whole, mangrove, salt marsh, and seagrass ecosystems are estimated to be disappearing from 2 to 15 times faster than terrestrial forests. Human activities are causing local eelgrass beds to disappear at a disturbing rate. Quantifying carbon storage potential in local eelgrass beds provides a valuable tool for assessing carbon stocks and highlighting priority areas for conservation.</p>
<p>MIT Sea Grant and MassBays are working together to develop outreach materials targeting community members that have an impact on eelgrass beds. These materials will help local conservation boards to understand their role in protecting these valuable coastal habitats, encourage beach goers to appreciate and explore eelgrass beds without harming them, and help teachers develop curricula where students can use real data to calculate carbon storage potential. Materials will be available this fall on the MIT Sea Grant website.</p>
<p>The work was carried out by a team of researchers that included: <a href="http://www.epa.gov/aboutepa/epa-region-1-new-england">EPA Region 1</a>, MIT Sea Grant, <a href="http://www.mass.gov/eea/agencies/mass-bays-program/">Massachusetts Bays National Estuary Program</a>, <a href="http://sites.bu.edu/novak/">Boston University</a>, <a href="http://www.suffolk.edu/">Suffolk University</a>, and <a href="http://www.mass.gov/eea/agencies/dfg/dmf/">Massachusetts Division of Marine Fisheries</a> with funding from the <a href="http://www.epa.gov/cre">U.S. Environmental Protection Agency Climate Ready Estuaries Program</a>, the <a href="http://mcnairscholars.com/">McNair Scholars Program</a>, and MIT Sea Grant.</p>
At the edge of an eelgrass bed, rocky sandy sediments appear in the foreground. Organic buildup of sediments under the vegetation can also be seen. MIT Sea Grant, Carbon, Environment, Ocean science, Research, Climate, Oceanography and ocean engineeringRogue wave aheadhttps://news.mit.edu/2016/prediction-tool-rogue-waves-0225
New prediction tool gives 2-3 minute warning of incoming rogue waves.Thu, 25 Feb 2016 00:00:00 -0500Jennifer Chu | MIT News Officehttps://news.mit.edu/2016/prediction-tool-rogue-waves-0225<p>Sailing history is rife with tales of monster-sized rogue waves — huge, towering walls of water that seemingly rise up from nothing to dwarf, then deluge, vessel and crew. Rogue waves can measure eight times higher than the surrounding seas and can strike in otherwise calm waters, with virtually no warning.</p>
<p>Now a prediction tool developed by MIT engineers may give sailors a 2-3 minute warning of an incoming rogue wave, providing them with enough time to shut down essential operations on a ship or offshore platform.</p>
<p>The tool, in the form of an algorithm, sifts through data from surrounding waves to spot clusters of waves that may develop into a rogue wave. Depending on a wave group’s length and height, the algorithm computes a probability that the group will turn into a rogue wave within the next few minutes.</p>
<p>“It’s precise in the sense that it’s telling us very accurately the location and the time that this rare event will happen,” says Themis Sapsis, the American Bureau of Shipping Career Development Assistant Professor of Mechanical Engineering at MIT. “We have a range of possibilities, and we can say that this will be a dangerous wave, and you’d better do something. That’s really all you need.”</p>
<p>Sapsis and former postdoc Will Cousins have published their results this week in the <em>Journal of Fluid Mechanics.</em></p>
<div class="cms-placeholder-content-video"></div>
<p><strong>“Not just bad luck”</strong></p>
<p>Like many complex systems, the open ocean can be represented as a chaotic mix of constantly changing data points. To understand and predict rare events such as rogue waves, scientists have typically taken a leave-no-wave-behind approach, in which they try to simulate every individual wave in a given body of water, to give a high-resolution picture of the sea state, as well as any suspicious, rogue-like activity. This extremely detailed approach is also computationally expensive, as it requires a cluster of computers to solve equations for each and every wave, and their interactions with surrounding waves.</p>
<p>“It’s accurate, but it’s extremely slow — you cannot run these computations on your laptop,” Sapsis says. “There’s no way to predict rogue waves practically. That’s the gap we’re trying to address.”</p>
<p>Sapsis and Cousins devised a much simpler, faster way to predict rogue waves, given data on the surrounding wave field.</p>
<p>In previous work, the team identified one mechanism by which rogue waves form in unidirectional wave fields. They observed that, while the open ocean consists of many waves, most of which move independently of each other, some waves cluster together in a single wave group, rolling through the ocean together. Certain wave groups, they found, end up “focusing” or exchanging energy in a way that eventually leads to an extreme rogue wave.</p>
<p>“These waves really talk to each other,” Sapsis says. “They interact and exchange energy. It’s not just bad luck. It’s the dynamics that create this phenomenon.”</p>
<p><strong>Going rogue</strong></p>
<p>In their current work, the researchers sought to identify precursors, or patterns in those wave groups that ultimately end up as rogue waves. To do this, they combined ocean wave data available from measurements taken by ocean buoys, with nonlinear analysis of the underlying water wave equations.</p>
<p>Sapsis and Cousins used the statistical data to quantify the range of wave possibilities, for a given body of water. They then developed a novel approach to analyze the nonlinear dynamics of the system and predict which wave groups will evolve into extreme rogue waves.</p>
<p>They were able to predict which groups turned rogue, based on two parameters: a wave group’s length and height. The combination of statistics and dynamics helped the team identify the length-scale of a critical wave group, which has the highest likelihood of evolving into a rogue wave. Using this, the team derived a simple algorithm to predict a rogue wave based on incoming data. By tracking the energy of the surrounding wave field over this length-scale, they could immediately calculate the probability of a rogue wave developing.</p>
<p>“Using data and equations, we’ve determined for any given sea state the wave groups that can evolve into rogue waves,” Sapsis says. “Of those, we only observe the ones with the highest probability of turning into a rare event. That’s extremely efficient to do.”</p>
<p>Sapsis says the team’s algorithm is able to predict rogue waves several minutes before they fully develop. To put the algorithm into practice, he says ships and offshore platforms will have to utilize high-resolution scanning technologies such as LIDAR and radar to measure the surrounding waves.</p>
<p>“If we know the wave field, we can identify immediately what would be the critical length scale that one has to observe, and then identify spatial regions with high probability for a rare event,” Sapsis says. “If you are performing operations on an aircraft carrier or offshore platform, this is extremely important.”</p>
<p>“The approach is original — it is fast, easy to implement, and it does not require computational power,” says Miguel Onorato, professor of physics at the University of Turin, who was not involved in the research. “Tests in wave basins and field measurements data are needed in order to establish reliability of the tool in realistic conditions.”</p>
<p>This research was supported in part by the Office of Naval Research, the Army Research Office, and the American Bureau of Shipping.</p>
“These waves really talk to each other,” Themis Sapsis says. “They interact and exchange energy. It’s not just bad luck. It’s the dynamics that create this phenomenon.”Image: MIT NewsClimate, Data, Earth and atmospheric sciences, Environment, Oceanography and ocean engineering, Physics, Research, Mechanical engineering, School of EngineeringLiving a “mixotrophic” lifestylehttps://news.mit.edu/2016/mixotrophic-plankton-ocean-carbon-storage-0201
Some tiny plankton may have big effect on ocean’s carbon storage.Mon, 01 Feb 2016 15:00:00 -0500Jennifer Chu | MIT News Officehttps://news.mit.edu/2016/mixotrophic-plankton-ocean-carbon-storage-0201<p>How do you find your food? Most animal species, whether they rummage through a refrigerator or stalk prey in the wild, obtain nutrients by consuming living organisms. Plants, for the most part, adopt a different feeding, or “trophic,” strategy, making their own food through photosynthesis. There are, however, certain enterprising species that can do both: photosynthesize and consume prey. These organisms, found mostly in certain ocean plankton communities, live a flexible, “mixotrophic” lifestyle.&nbsp;</p>
<p>Now researchers at MIT and Bristol University in the United Kingdom have found that these microscopic, mixotrophic organisms may have a large impact on the ocean’s food web and the global carbon cycle.&nbsp;</p>
<p>The scientists developed a mixotrophic model of the global ocean food web, at the scale of marine plankton, in which they gave each plankton class the ability to both photosynthesize and consume prey. They found that, compared with traditional models that do not take mixotrophs into account, their model produced larger, heavier plankton throughout the ocean. As these more substantial microbes die, the researchers found they increase the flux of sinking organic carbon particles by as much as 35 percent.</p>
<p>The results, says Mick Follows, associate professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences, suggest that mixotrophic organisms may make the ocean more efficient in storing carbon, which in turn enhances the efficiency with which the oceans sequester carbon dioxide.</p>
<p>“If [mixotrophs] weren’t in the oceans, we’re suggesting atmospheric carbon dioxide might be higher, because there would less of the large, carbon-rich particles formed which efficiently transfer carbon to depth,” Follows says. “It’s a hypothesis, but it has been ignored in carbon cycle models until now, and we suggest it must be represented because it’s potentially very important.”</p>
<p>Follows and his colleague Ben Ward, a former MIT postdoc now at Bristol University, have published their results today in the <em>Proceedings of the National Academy of Sciences.</em></p>
<p><strong>Part of the equation</strong></p>
<p>Today’s ocean models typically take an “either/or” approach, grouping plankton as either photosynthesizers or consumers of prey. This approach, Follows says, oversimplifies the processes taking place in the ocean that may ultimately contribute to how carbon moves through the oceans and atmosphere. He says mixotrophs are often overlooked, because our terrestrial experience makes them seem rare.&nbsp;</p>
<p>“To us on land, we tend to think of [mixotrophs], like Venus fly traps, as exotic — they are a curiosity to us,” Follows says. “Our traditional perspective is biased by the land, where organisms fall into one or the other category, rather strictly. But in the oceans, the more people have looked at plankton, the more mixotrophy seems to be common.”&nbsp;</p>
<p>The problem is that there are very few data to work into models, as it’s extremely difficult to observe trophic strategies at the microscopic plankton scale. Therefore, models have largely left mixotrophs out of the equation and have instead looked to other marine processes to try and explain how much carbon is stored in the oceans.&nbsp;</p>
<p>“It’s like if we have a weather forecast model that gets the rain right in Boston today, but for the wrong reasons,” Follows says. “If we use it tomorrow, we shouldn’t expect it to do a good job, because it was cooked up for today. We want our climate model to be representative of the processes going on, in order to be predictive of how carbon storage responds to global change.”</p>
<p><strong>Making a (mixotrophic) living</strong></p>
<p>As a first step, Follows and Ward chose to simulate a virtual world in which every plankton class is potentially mixotrophic.&nbsp;</p>
<p>“It’s a very idealized, black-and-white case: What’s the maximum impact mixotrophs could have?” Follows says.&nbsp;</p>
<p>In the oceans, plankton can range in size from less than 1 micron, to about 1 millimeter in diameter. Typical ocean models that incorporate plankton often group them in 10 general size classes, each of which fall into a “two-guild” structure, as either photosynthesizers, or consumers of prey.&nbsp;</p>
<p>Instead, Follows and Ward made all of the plankton mixotrophic. The organisms in the model can photosynthesize, consuming inorganic nutrients. (The smallest organisms are the most efficient at acquiring those resources.) They can also eat other plankton and are constrained to consume prey in size classes about ten times smaller than themselves.</p>
<p>“After we have built in these rules for the system, whether each size class lives largely by photosynthesis or largely by predation depends upon the availability of each type of resource and their relative ability to harvest them in each environment,” Follows says.</p>
<p>After running the model forward, the researchers compared the results to those of a traditional model without mixotrophs. They found both models showed a general feeding structure throughout the plankton food web: The smallest organisms were too small to ingest prey, while the largest plankton were poor competitors when living by photosynthesis.&nbsp;</p>
<p>However, where the traditional model made a strict separation between those that photosynthesize and those that don’t, the mixotrophic model blurred those lines, with some smaller organisms consuming prey and some larger ones being able to photosynthesize. The result was that mixotrophic organisms in every class increased the average size of that organism, creating larger and heavier plankton throughout the oceans. These more substantial organisms, compared to smaller and lighter plankton, were more capable of sinking to the ocean floor, as carbon-containing detritus.</p>
<p>“It essentially means that, through multiple means, in a world with mixotrophs, more organic carbon is sinking into the deep ocean than in a world without mixotrophs,” Follows says.&nbsp;</p>
<p>The team’s estimate of the amount of sinking carbon contributed by mixotrophs appears to agree with recent observations of carbon flux by mixotrophic plankton in the North Atlantic. Follows says that, with more data on these opportunistic organisms, he hopes to improve the model to accurately reflect mixotrophic populations and their effect on the planet’s carbon cycle.</p>
<p>“Part of our hope is for the work is to give some wind to the sails of these observational studies. We think they’re very valuable,” Follows says. “There may be a large fraction of grazing that is being done by mixotrophs, so it’s potentially very significant in terms of the flow of carbon in the ocean and it should be quantified.”</p>
<p>This research was funded, in part, by the Simons Foundation, the Gordon and Betty Moore Foundation, NASA, and the National Science Foundation.</p>
“If (mixotrophs) weren’t in the oceans, we’re suggesting atmospheric carbon dioxide might be higher, because there would less of the large, carbon rich particles formed which efficiently transfer carbon to depth,” Mick Follows says. Image: James Fraser/Biodiversity Heritage LibraryEarth and atmospheric sciences, EAPS, Oceanography and ocean engineering, Climate, Climate change, Biology, National Science Foundation (NSF), NASA, School of ScienceQ&amp;A: Visiting artist Keith Ellenbogen https://news.mit.edu/2015/cast-visiting-artist-keith-ellenbogen-brings-high-speed-photography-natural-world-1124
MIT Center for Art, Science, and Technology visiting artist Keith Ellenbogen brings high-speed photography to the natural world.Tue, 24 Nov 2015 14:04:01 -0500Hannah Hailan Pang | Edgerton Centerhttps://news.mit.edu/2015/cast-visiting-artist-keith-ellenbogen-brings-high-speed-photography-natural-world-1124<p><em>Walk down MIT’s Infinite Corridor, or through some lesser-known hallways, or even many offices around campus, and you’ll find framed prints of some of Harold “Doc” Edgerton’s famous high-speed photography: a bullet through an apple, a pole vaulter arching his body with athletic perfection, a milk drop exploding in mid-air.</em></p>
<p><em>As the instructor for 6.163 (Strobe Project Lab), Edgerton Center Associate Director Jim Bales continues Edgerton’s legacy in high-speed imaging. And Keith Ellenbogen, a Center for Art, Science and Technology (CAST) Visiting Artist, has set up camp in shared office space with Bales. His focus: high-speed marine photography.</em></p>
<p><em>Ellenbogen’s work has received international acclaim in underwater photography and video, with a focus on conservation efforts. His residency with CAST spans this semester and the upcoming Independent Activities Period (IAP), during which he is working closely with Bales and associate professor of physics Allan Adams to create emotionally charged underwater photography using high-speed imaging and other technologies. Keith hopes to teach students about photography, especially the ways environmental photography can inspire conservation efforts. He recently answered a few questions about his residency.</em></p>
<p><strong>Q: </strong>Where did you get your start in underwater photography?</p>
<p><strong>A: </strong>I grew up in Newton, Massachusetts, and started volunteering at the [New England] Aquarium when I was 16. Actually, I got my start in diving and learning about animals there, especially learning about each animal’s role in the ocean. When I became interested in photography, naturally I began experimenting there first, and my friends and mentors who helped me get started were crucial to the start of my career.</p>
<p><strong>Q:</strong> How did you get into the high-speed imaging projects with Allan Adams?</p>
<p><strong>A: </strong>Well, fast-forward a number of years, and long story short, Allan was really interested in my work — and vice versa — when we happened to meet at an event in 2012. He invited Jim [Bales] and myself to his house for brunch, and it became that cool thing when you put some heads together and awesome ideas come out of it. Jim had the imaging expertise, advice, and all the connections in the high-speed world. We were so excited to hear him say, “These ideas sound cool. Let’s do it!”</p>
<p><strong>Q: </strong>Can you describe a bit how you and Adams play off of each other for the work?</p>
<p><strong>A: </strong>Absolutely – I couldn’t have this residency [at MIT] without this collaboration with Allan, where we’re essentially pushing each other to the best we can do. Allan, of course, knows a crazy amount about quantum mechanics and theoretical physics. One idea we had a couple of years ago was to high-speed photograph cuttlefish. When cuttlefish strike their prey, they can move incredibly fast, but actually stop right before they reach prey. Otherwise they’d pierce through it. But you can’t see this with the human eye. Allan knew all about it and about how their motions can be described by physics, and said, why not try using high-speed imaging to illuminate what we can’t see? I was really excited by it, so we went down to the aquarium to try this. In the end, after a long time setting up and shooting and shooting again, we got these brilliant snaps of each part of the cuttlefish’s movement.</p>
<p><strong>Q:</strong> It must be hard to get good shots! How do you do it?</p>
<p><strong>A: </strong>Yeah, it takes at least weeks! Often months. There’s getting the equipment, setting it up, getting crew to travel over. In the aquarium, I can’t go in the water with the strobe imaging equipment, so there’s the added difficulty of waiting for animals, without being able to go towards them.</p>
<p>One time we wanted to shoot the Van de Graff generator in the Museum of Science shooting sparks. It happens in real life in a millionth of a second, so to watch the spark form we needed a camera that can take 10 million frames per second. Ten million requires very special equipment! We usually only have cameras that capture thousands of frames per second. This one took a couple of months to get done. But we got some crazy, just the coolest photos. I think we all got goosebumps when we saw the lines of sparks crawling through the air in the photo. Another example of the work that came from Allan and I brainstorming, bouncing ideas off of one another.</p>
<p>Also, as a photographer, I have to think about what to go for, how long to wait, especially when I’m out in the field waiting for animals to do something like catch food. Sometimes I only have a couple of days on a project, so strategizing comes into play. This is one of those things that gets easier with practice and experience, but there’s always a stressful, tense sort of thrill whenever I’m on a project.</p>
<p><strong>Q: </strong>Tell me a bit about what you’re hoping to do at MIT.</p>
<p><strong>A: </strong>The biggest is teaching the IAP course with Allan: Underwater Conservation Photography. We start with the basics of photography, and at the end we’re taking the class to Belize to shoot in the field. I want to teach how to show the world through the lens and influence conservation with it. I love teaching, and I think Allan and I will have a ton of fun with it. I hope the students can get a lot out of it too.</p>
<p>Another, of course, is being around the people. Jim is an invaluable mentor, and has so many contacts in the imaging world. Being in the Edgerton Center itself around the history of photography that started from here is inspiring.</p>
<p><strong>Q: </strong>What would you tell someone who asks you how photographs influence conservation? What is something about it that you’d want all of us to know?</p>
<p><strong>A: </strong>It’s been a big part of my career. It’s the aesthetic of a photo that makes it easy for people to relate to, and once that emotional connection is made, people will care; they’ll be moved and feel compelled to do something. I think photos have such huge potential because everything about them — composition, subject matter, etc. — can be learned and used to the best way to captivate the audience. And now, using the intersection of technology and photography, we uncover yet another world to learn new things: seeing things we literally could not before, and learning new things about animals and giving them a voice that they didn’t have before. I’d say it’s a very powerful tool.</p>
MIT Visiting Artist Keith Ellenbogen photographed large school of golden sweepers within a coral reef in Palau.Keith Ellenbogen/iLCPCenter for Art, Science and Technology, Arts, Edgerton, Photography, Conservation, Oceanography and ocean engineering, Independent Activities Period, Classes and programsCapturing an underwater worldhttps://news.mit.edu/2015/capturing-underwater-world-keith-ellenbogen-1117
Visiting artist Keith Ellenbogen collaborates with MIT faculty and staff to create a unique underwater photography course.Tue, 17 Nov 2015 17:57:01 -0500Cassie Martin | Oceans at MIThttps://news.mit.edu/2015/capturing-underwater-world-keith-ellenbogen-1117<p>Keith Ellenbogen is a renowned underwater photographer and adventurer. He has spent his career documenting marine life — from Palau’s coral reefs to migrating bluefin tuna in the Mediterranean — not only to showcase their beauty, but also to inspire social change and action toward protecting the delicate underwater environments in which they live.</p>
<p>“As a photographer I can create a level of compassion and engagement in my images that is further supported by science and conservation efforts,” he says. “Hopefully these images connect with people quickly and viscerally, and motivates them to protect these places, create awareness, and change policies.”</p>
<p>Now, <a href="http://arts.mit.edu/artists/keith-ellenbogen/" target="_blank">Ellenbogen</a> has brought his talents to MIT as a&nbsp;visiting artist&nbsp;with the Center for Art, Science, and Technology (CAST). In collaboration with&nbsp;<a href="http://edgerton.mit.edu/high-speed-imaging" target="_blank">Edgerton Center</a>&nbsp;Associate Director Jim Bales and theoretical physicist Allan Adams, Ellenbogen is exploring new high-speed photography and underwater imaging techniques, developing cutting-edge technology, and preparing to share his passion for marine conservation with MIT students in an upcoming Independent Activities Period (IAP) course. “When you put people together and you can create a place that allows ideas to really grow, it’s the most wonderful thing,” he says of the CAST&nbsp;program.</p>
<p><strong>Physics meets photography</strong></p>
<p>Although Ellenbogen has been photographing since he was a young boy, MIT physicist Allan Adams’ first introduction to high-speed imaging came in 2011. He worked with Jim Bales of the MIT Edgerton Center to photograph the high-speed collision of a cookie and a potato pancake for&nbsp;MIT’s <a href="http://hillel.mit.edu/content/latke-vs-hamentaschen" target="_blank">Great Latke vs. Hamentashen Debate</a> — a humorous academic event held to determine which traditional Jewish food is superior. The experience left Adams wanting more, and when he met Ellenbogen through mutual friends, a lightbulb went off. “Keith is a master underwater photographer, and Jim is a master image maker at the edge of technology,” Adams says. “Clearly these two worlds should play together.”</p>
<p>And play together they did. Adams and Ellenbogen, with support from the Edgerton Center and Tech Imaging Services Inc., filmed a variety of New England Aquarium underwater residents, including sharks, lionfish, and cuttlefish, at 1,200 frames per second in high definition. The resulting slow-motion videos revealed the awe-inspiring complexity of these creatures’ movements and behaviors, and were featured in a 2013 NEAQ exhibition&nbsp;“<a href="http://oceans.mit.edu/news/featured-stories/invisible-ocean" target="_blank">The Invisible Ocean—Extreme Time</a>,” as well as various advertising campaigns. They continue working together, and recently returned from a trip to Patagonia, where they taught a course on wildlife conservation photography focusing on animals at the intersection of land and sea — specifically, penguins, elephant seals, and right whales.</p>
<p>“The collaboration and synergy between [Adams, Bales, and myself] is wonderful. We each bring our own expertise to the table and push each other in different ways,” Ellenbogen says. At MIT, the team is using that synergy to develop new technology that’s still under wraps. “We are exploring the role of which photography doesn’t have to be only in a straightforward linear path,” he says. “We are working together to push the boundaries of where we really are right now.” Ellenbogen added that the team hopes to demonstrate some initial prototypes and showcase the resulting images through the IAP course.</p>
<p><strong>From Boston to Belize</strong></p>
<p>Starting in January, students will have the opportunity to work with the team in an all-expenses-paid “Underwater Conservation Photography” course. “We’ll be teaching students everything from camera settings to how to build lighting systems for underwater work to building ROVs,” Adams says, referring to remotely operated vehicles. Students will spend three weeks in Boston learning new skills, working on the available technology, and testing out their equipment in pools and aquariums before heading south, where they will spend a week with the Wildlife Conservation Society on&nbsp;<a href="http://www.wcsgloversreef.org/" target="_blank">Glover’s Reef</a>&nbsp;off the coast of Belize.</p>
<p>“Students will team up with scientists who will explain the animals and the research they’re doing,” Ellenbogen says. “[They] will photograph individual animals for aesthetic purposes as well as to tell a conservation story or narrative that helps explain why the animals are significant.”</p>
<p>The resulting images will become part of an exhibition that will travel to museums, zoos, aquariums, and colleges around the world. An accompanying app will also allow visitors walking through the gallery to look up images to see their backstory and commentary from students. Eventually, the content from the app will serve as a permanent online exhibition.</p>
<p>“Part of creating science and art is creating things that you share and communicate. An image or an idea that remain in your head for all practical purposes don’t exist in the world,” Adams said. “The whole point of the course is to encourage students to think about the ways they can use visual culture and technology to communicate things that matter — ideas about conservation, ideas about science, and just beautiful things. It’s all about communicating. The concrete goal of having an image that will go out into the world is central to that.”</p>
<p>Spots in the class are still available as of press time, and the&nbsp;<a href="https://docs.google.com/forms/d/1wFXiCtkBEPYVMEN117mE-s5w7Ki8g2Ck4_7guRGyU7w/viewform?c=0&amp;w=1" target="_blank">application</a>&nbsp;deadline is Dec. 4.</p>
California sea lions near the kelp forests off the coast of Monterey, CaliforniaKeither EllenbogenCenter for Art, Science and Technology, Arts, Edgerton, Photography, Conservation, Oceanography and ocean engineering, Independent Activities Period, Classes and programsTo capture a wavehttps://news.mit.edu/2015/capturing-waves-themistoklis-sapsis-1016
Themistoklis Sapsis seeks to understand, predict, and optimize complex engineering and environmental systems under extreme uncertainty.Fri, 16 Oct 2015 12:45:01 -0400Steve Calechman | MIT Industrial Liaison Programhttps://news.mit.edu/2015/capturing-waves-themistoklis-sapsis-1016<p>Creating anything new requires testing the limits of what already exists and delving into uncertainty. This is what Themistoklis Sapsis does regularly. “My work is on systems for which we understand as much as we don’t understand,” the assistant professor of mechanical engineering and director of the <a href="http://sandlab.mit.edu/" target="blank">Stochastic Analysis and Nonlinear Dynamics Lab</a>&nbsp;says.&nbsp;By using analytical and computational methods, Sapsis tries to predict and optimize behavior, particularly when the dynamics and excitations are uncertain and occasionally extreme. This places much of his work in the ocean environment, and whether it’s an energy-harvesting configuration or an ocean structure, his goal is to create designs that maintain operational robustness and safety regardless of the constantly varying conditions.</p>
<p><strong>Designing a better boat</strong></p>
<p>A typical example of Sapsis’ work is analyzing the behavior of a ship in extreme weather. It’s a system and environment that combines nonlinear dynamics and uncertainty. The latter is caused by the broad range of possible conditions that a ship can encounter and results in the greatest range of possible outcomes that run from benign to catastrophic, he says. The former is an element that’s often overlooked but essential for the realistic description of the ship’s behavior. By studying them together, the potential increases for being able to produce a better structure. However, the computational cost of such analysis is often prohibitive even with modern capabilities, Sapsis says.</p>
<p>In ship design, there are certain known factors, such as dimensions and hull geometry. There are also less predictable elements, such as the intensity of water crashing into the front and sides. Add to that the possibility of extreme weather. It’s not a regular occurrence, but it will happen, and when it does, a ship needs to be able to perform reliably. What’s needed, Sapsis says, is the development of new mathematical methods that will be able to define the envelope of safe operations, taking into account even rare events. In order to achieve such a goal, one has to focus on the statistics of the response, which indirectly describe all possible scenarios, rather than the isolated analysis of every possible outcome, which would be prohibitively expensive, he says.</p>
<p>Along with the advantage of taking into account even rare events, Sapsis’ approach brings other advantages. He focuses on developing algorithms inexpensive enough so they can run off of a laptop, rather than a cluster of computers, keeping costs to a minimum. That freedom and flexibility lead to a more efficient and safe design. “It means less cost, higher speed and higher reliability,” Sapsis says.</p>
<p><strong>Taking motion, making power</strong></p>
<p>Sapsis also works on energy harvesting, particularly as it relates to powering small electronic devices. The same challenges apply as with a ship in the ocean: He looks at an excitation that varies in its occurrence and intensity. Using nonlinear configurations in this realm allows him to not rely on the energy content of a specific frequency, giving a broader range of resonances, he says.</p>
<p>Through a “carefully designed oscillator,” Sapsis says that his group is looking to capture energy from walking, walking quickly, and running. These three motions have completely different characteristics, and a traditional approach relying on linear oscillators would require a separate set of design parameters for each case. Using nonlinear mechanical oscillators capable of adaptively resonating with the different paces, kinetic energy would be absorbed and transformed into electromagnetic energy with a robust level of efficiency, ultimately extending the cell battery’s life, he says.</p>
<p>The challenge, much like with dealing with ocean waves, is in the characteristics of the excitation. Kinetic energy doesn’t always efficiently covert into usable energy. Because different people produce different accelerations when they move, Sapsis says that his design goal is fairly simple: to create consistency and maintain robustness. To do that, he needs a model, and he’s chosen a ubiquitous one. “We are inspired by what nature does,” Sapsis says, noting that turbulence, found in atmospheric and oceanic flows, is an example of robust energy transfer from scale-to-scale that he’s trying to mimic in mechanical settings.</p>
<p><strong>The need for some pushing</strong></p>
<p>Like many of his MIT colleagues, Sapsis work applies to a range of industries: design of ships and offshore structures, reliability of communication and power networks, energy harvesting, and vibration mitigation. The one consistent element is the need for collaboration. Sapsis says that while academia and industry are inclined to have an initial mutual reticence, there are benefits from both sides moving closer to each other. Academia can explore issues that aren’t merely theoretical or niche-based but address a larger market need, and industry gets to train the next generation of engineers.</p>
<p>Sapsis adds that more than merely co-existing, there’s a greater opportunity to be taken. The two realms need to brainstorm common-interest problems and push themselves to explore issues that aren’t usually touched upon, especially ones that incorporate the uncertainty factor into design principles. Doing that will both produce stronger results for a given project and ingrain a mentality and higher expectations for future work. “We have to go beyond the low hanging fruit,” Sapsis says.</p>
MIT Department of Mechanical Engineering Assistant Professor Themistoklis SapsisDavid SellaFaculty, Profile, Mechanical engineering, Oceanography and ocean engineering, Ocean modeling, IndustryArtificial whisker reveals source of harbor seal’s uncanny prey-sensing abilityhttps://news.mit.edu/2015/whisker-slaloming-harbor-seal-catch-prey-1016
Study finds a whisker’s “slaloming” motion helps seals track and chase prey.Thu, 15 Oct 2015 23:59:59 -0400Jennifer Chu | MIT News Officehttps://news.mit.edu/2015/whisker-slaloming-harbor-seal-catch-prey-1016<p>Harbor seals have an amazingly fine-tuned sense for detecting prey, as marine biologists have noted for years. Even when blindfolded, trained seals are able to chase the precise path of an object that swam by 30 seconds earlier. Scientists have suspected that the seal’s laser-like tracking ability is due in part to its antennae-like whiskers.</p>
<p>Now engineers at MIT have fabricated and tested a large-scale model of a harbor seal’s whisker, and identified a mechanism that may explain how seals sense their environment and track their prey.</p>
<p>The team found that a seal’s whiskers serve two main functions in sensing the environment: first remaining still in response to a seal’s own movements through the water, and then oscillating in a “slaloming” motion in response to the turbulence left by a moving object.</p>
<p>In their experiments, the researchers observed that once the fabricated whisker enters the wake left by a passing object, it starts vibrating at the same frequency as the wake’s passing vortices. Careful visualizations show that the whisker “slaloms” among the vortices, like a skier zigzagging between flags.</p>
<p>The research shows that this slaloming allows the whisker to extract energy from the wake, causing it to vibrate at the precise frequency of the wake — a mechanism that may give seals a clue to an object’s path, its size, and even its shape.</p>
<p>Michael Triantafyllou, the William I. Koch Professor in MIT’s Department of Mechanical Engineering, says that biologically inspired sensors, modeled after the harbor seal’s whiskers, may aid underwater vehicles in tracking schools of fish, as well as sources of pollution — a goal that he is currently working toward.</p>
<p>He and former graduate student Heather Beem, whose PhD thesis formed the basis of the work, have published their results in the <em>Journal of Fluid Mechanics.</em></p>
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<p><strong>A “quieting effect”</strong></p>
<p>The harbor seal’s whiskers are unique in shape: Even to the naked eye, an individual whisker appears not uniform, but wavy. Under a magnifying glass, the pattern is more intricate, with an elliptical cross-section that varies in size along its span.</p>
<p>“It’s marvelous to see this intricate pattern, it’s not just a straight antenna — it’s a perfect sinusoid,” Triantafyllou says.</p>
<p>He and Beem proposed that a whisker’s curiously geometric morphology may play a part in a seal’s exceptional sensitivity.</p>
<p>Using 3-D printing techniques, Beem reproduced the seal’s wavy morphology at a much larger scale, in order to accurately measure its response to various wakes. She tested the whisker’s vibration properties in a 30-meter-long tank of water with a moving track suspended above the water.</p>
<p>In her experiments, Beem first attached the artificial whisker to the moving track, allowing the whisker to freely vibrate in the water as it moved down the length of the tank.</p>
<p>While most long, thin rods tend to create large vortices, or eddies, as they move through water, forming a pattern that’s well-known in fluid mechanics, Beem found that the wavy pattern of the whisker’s geometry created much weaker vortices, enabling the whisker to move silently, with very little vibration, through the water.</p>
<p>The whisker’s morphology, the researchers found, may help the seal block out its own disturbance as it moves through water.</p>
<p>“It’s like having the ability to stick your head out of a car window, and have there be no noise, so that your ears don’t ring: It’s a quieting effect,” Triantafyllou says.&nbsp;</p>
<p><strong>A whisker sensor</strong></p>
<p>To test how a whisker reacts to external stimuli, Beem conducted a second set of experiments in which she attached a large, long circular cylinder ahead of the whisker. As the cylinder moved down the tank, it created large eddies, similar to the patterns generated by a passing fish.</p>
<p>In response, she found that the whisker, when following the cylinder, vibrated significantly, moving in a slaloming pattern among the wake vortices. As she varied the speed of the moving track, the whisker quickly adapted, vibrating at precisely the frequency of the cylinder’s changing vortices. &nbsp;</p>
<p>“The geometry of the whisker allows for this phenomenon of being able to move very silently through the water if the water’s calm, and extract energy from the fish’s wake in order to vibrate a lot,” Beem says. “Now we have an idea of how it’s possible that seals can find fish that they can’t see.”</p>
<p>Triantafyllou says artificial whiskers may be useful as low-power sensors for underwater vehicles.</p>
<p>“We already have a few sensors that can detect velocity, but now that we know better what they can do, we can use them to track sources of pollution and the like,” Triantafyllou says. “By having several whiskers on a vehicle, like the seal, you can, for example, detect a faraway plume, and track it all the way to the end.”</p>
<p>This research was supported in part by the Office of Naval Research, the Singapore-MIT Alliance for Research and Technology, and the MIT Sea Grant program.</p>
Energy, Oceanography and ocean engineering, Research, Robots, Robotics, Mechanical engineering, School of EngineeringFertilize the ocean, cool the planet?https://news.mit.edu/2015/fertilize-ocean-cool-planet-0908
MIT researchers find unintended consequences of an idea to stimulate ocean phytoplankton growth in order to geoengineer a cooler atmosphere.Tue, 08 Sep 2015 15:11:01 -0400Mark Dwortzan | Joint Program on the Science and Policy of Global Changehttps://news.mit.edu/2015/fertilize-ocean-cool-planet-0908<p>Like the leaves of New England maples, phytoplankton, the microalgae at the base of most oceanic food webs, photosynthesize when exposed to sunlight. In the process, they absorb carbon dioxide from the atmosphere, converting it to carbohydrates and oxygen. Many phytoplankton species also release dimethyl sulfide (DMS) into the atmosphere, where it forms sulfate aerosols, which can directly reflect sunlight or increase cloud cover and reflectivity, resulting in a cooling effect. The ability of phytoplankton to draw planet-warming carbon dioxide (CO<sub>2</sub>) from the atmosphere and produce aerosols that promote further cooling has made ocean fertilization — through massive dispersal of iron sulfite and other nutrients that stimulate phytoplankton growth — an attractive geoengineering method to reduce global warming.</p>
<p>But undesirable climate impacts could result from such a large-scale operation, which would significantly increase emissions of DMS, the primary source of sulfate aerosol over much of the Earth’s surface, and a key player in the global climate system. Now, in a <a href="http://www.nature.com/articles/srep13055" target="_blank">study</a> published in <em>Nature’s Scientific Reports, </em>MIT researchers found that enhanced DMS emissions, while offsetting greenhouse gas-induced warming across most of the world, would induce changes in rainfall patterns that could adversely impact water resources and livelihoods in some regions.</p>
<p>“Discussions of geoengineering are gaining ground recently, so it’s important to understand any unintended consequences,” says Chien Wang, a co-author of the study and a senior research scientist at MIT’s Center for Global Change Science and the Department of Earth, Atmospheric, and Planetary Sciences. “Our work is the first in-depth analysis of ocean fertilization that has highlighted the potential danger of impacting rainfall adversely.”</p>
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<p>To investigate the impact of enhanced DMS emissions on global surface temperature and precipitation, the researchers used one of the <a href="http://www2.cesm.ucar.edu/" target="_blank">global climate models</a> used by the Intergovernmental Panel on Climate Change (IPCC), which simulates the evolution of and interactions among the ocean, atmosphere, and land masses. Running simulations that compared two scenarios, they found mixed results. In one simulation they implemented a scenario known as <a href="http://asr.science.energy.gov/publications/program-docs/RCP4.5-Pathway.pdf">RCP4.5</a> that is used by the IPCC to project greenhouse gas concentrations, aerosol emissions, and land-use change based on policies that lead to moderate mitigation of greenhouse gas emissions over the course of the 21st century. They also used RCP4.5 in a second simulation, with one exception: DMS emissions from the ocean were increased to the maximum feasible levels, or about 2.5 times higher.</p>
<p>The simulations showed that enhanced DMS emissions would reduce the increase in average global surface temperature to half that of the RCP4.5 scenario, resulting in a net increase of 1.2 degrees Celsius by 2100. But the cost would be a substantial reduction in precipitation for some regions.</p>
<p>“Generally, our results suggest that the cooling effect associated with enhanced DMS emissions would offset warming across the globe, especially in the Arctic,” says the study’s first author, Benjamin Grandey, a senior postdoc in Wang’s group who configured the model simulations and analyzed the data. “Precipitation would also decline worldwide, and some parts of the world would be worse off.&nbsp; Europe, the Horn of Africa, and Pakistan may receive less rainfall than they have historically.”</p>
<p>Grandey and Wang warn that the lower rainfall could reduce water resources considerably, threatening the hydrological cycle, the environment, and livelihoods in the affected regions.</p>
<p>The researchers hope their investigation will inspire further studies of more realistic ocean fertilization scenarios, and of the potential impacts on marine ecosystems as well as human livelihoods. Further research will be needed, they say, to fully evaluate the viability of ocean fertilization as a geoengineering method to offset greenhouse gas-induced warming.</p>
<p>The study was funded by the Singapore National Research Foundation through the Singapore-MIT Alliance for Research and Technology Center for Environmental Sensing and Modeling, and grants from the National Science Foundation, Department of Energy, and Environmental Protection Agency.&nbsp;</p>
A large phytoplankton bloom off the coast of PortugalJacques Descloitres/NASA Goddard Space Flight CenterJoint Program on the Science and Policy of Global Change, Climate, Climate change, Environment, Sustainability, Research, Civil and environmental engineering, EAPS, Earth and atmospheric sciences, Policy, Phytoplankton, Oceanography and ocean engineering, Singapore-MIT, National Science Foundation (NSF), Department of Energy (DoE), Energy, Greenhouse gases